861 lines
34 KiB
XML
861 lines
34 KiB
XML
<!-- faq-programming.xml -->
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<qandaentry id="faq.programming.packages">
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<question><para>How do I contribute a package?</para></question>
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<answer>
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<para>If you are willing to be a package maintainer, great! We urgently need
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volunteers to prepare and maintain packages, because the priority of the
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Cygwin Team is Cygwin itself.
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</para>
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<para>The Cygwin Package Contributor's Guide at
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<ulink url="http://cygwin.com/setup.html">http://cygwin.com/setup.html</ulink> details everything you need to know
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about being a package maintainer. The quickest way to get started is to
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read the <emphasis>Initial packaging procedure, script-based</emphasis> section on
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that page. The <literal>generic-build-script</literal> found there works well for
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most packages.
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</para>
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<para>For questions about package maintenance, use the cygwin-apps mailing
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list (start at <ulink url="http://cygwin.com/lists.html">http://cygwin.com/lists.html</ulink>) <emphasis>after</emphasis>
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searching and browsing the cygwin-apps list archives, of course. Be
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sure to look at the <emphasis>Submitting a package</emphasis> checklist at
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<ulink url="http://cygwin.com/setup.html">http://cygwin.com/setup.html</ulink> before sending an ITP (Intent To
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Package) email to cygwin-apps.
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</para>
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<para>You should also announce your intentions to the general cygwin list, in
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case others were thinking the same thing.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.contribute">
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<question><para>How do I contribute to Cygwin?</para></question>
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<answer>
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<para>If you want to contribute to Cygwin itself, see
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<ulink url="http://cygwin.com/contrib.html">http://cygwin.com/contrib.html</ulink>.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.huge-executables">
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<question><para>Why are compiled executables so huge?!?</para></question>
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<answer>
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<para>By default, gcc compiles in all symbols. You'll also find that gcc
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creates large executables on UNIX.
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</para>
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<para>If that bothers you, just use the 'strip' program, part of the binutils
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package. Or compile with the <literal>-s</literal> option to gcc.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.glibc">
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<question><para>Where is glibc?</para></question>
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<answer>
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<para>Cygwin does not provide glibc. It uses newlib instead, which provides
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much (but not all) of the same functionality. Porting glibc to Cygwin
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would be difficult.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.objective-c">
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<question><para>Where is Objective C?</para></question>
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<answer>
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<para>Objective C hasn't been distributed with the Cygwin version of gcc
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for a long time. For several reason Cygwin was stuck with gcc version 3.4.4.
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Fortunately the latest gcc maintainer is quite busy to create a working
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gcc 4.x release which also comes with an Objective C package.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.make-execvp">
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<question><para>Why does my make fail on Cygwin with an execvp error? </para></question>
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<answer>
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<para>First of all, if you are using <literal>make -j[N]</literal>, then stop. It doesn't
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work well. Also beware of using non-portable shell features in your
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Makefiles (see tips at <ulink
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url="http://cygwin.com/faq/faq.using.html#faq.using.shell-scripts" />).
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</para>
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<para>Errors of <literal>make: execvp: /bin/sh: Illegal Argument</literal> or
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<literal>make: execvp: /bin/sh: Argument list too long</literal> are often
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caused by the command-line being to long for the Windows execution model.
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To circumvent this, mount the path of the executable using the -X switch
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to enable cygexec for all executables in that folder; you will also need
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to exclude non-cygwin executables with the -x switch. Enabling cygexec
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causes cygwin executables to talk directly to one another, which increases
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the command-line limit. To enable cygexec for <literal>/bin</literal> and
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<literal>/usr/bin</literal>, you can add or change these entries in /etc/fstab:
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</para>
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<screen>
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C:/cygwin/bin /bin ntfs binary,cygexec 0 0
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C:/cygwin/bin /usr/bin ntfs binary,cygexec 0 0
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</screen>
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<para>Note that if you have Tcl/Tk installed, you must additionally
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exclude <literal>tclsh84</literal> and <literal>wish84</literal>, which
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are linked to the Cygwin DLL but are not actually Cygwin programs:
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</para>
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<screen>
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C:/cygwin/bin/tclsh84.exe /bin/tclsh84.exe ntfs binary,notexec 0 0
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C:/cygwin/bin/tclsh84.exe /usr/bin/tclsh84.exe ntfs binary,notexec 0 0
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C:/cygwin/bin/wish84.exe /bin/wish84.exe ntfs binary,notexec 0 0
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C:/cygwin/bin/wish84.exe /usr/bin/wish84.exe ntfs binary,notexec 0 0
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</screen>
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<para>If you have added other non-Cygwin programs to a path you want to mount
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cygexec, you can find them with a script like this:
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</para>
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<screen>
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#!/bin/sh
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cd /bin; for f in `find . -type f -name '*.exe'`; do
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cygcheck $f | (fgrep -qi cygwin1.dll || echo $f)
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done
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</screen>
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<para>
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See <ulink url="http://cygwin.com/cygwin-ug-net/using.html#mount-table" />
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for more information on using mount.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.ipc">
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<question><para>How can I use IPC, or why do I get a <literal>Bad system call</literal>
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error?</para></question>
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<answer>
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<para>
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Try running cygserver. Read
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<ulink url="http://cygwin.com/cygwin-ug-net/using-cygserver.html" />. If you're
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trying to use PostgreSQL, also read
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<literal>/usr/share/doc/Cygwin/postgresql-*.README</literal>.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.winmain">
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<question><para>Why the undefined reference to <literal>WinMain@16</literal>?</para></question>
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<answer>
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<para>If you're using <literal>gcc</literal>, try adding an empty main() function to one
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of your sources. Or, perhaps you have <literal>-lm</literal> too early in the
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link command line. It should be at the end:
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</para>
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<screen>
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bash$ gcc hello.c -lm
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bash$ ./a.exe
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Hello World!
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</screen>
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<para>works, but
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</para>
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<screen>
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bash$ gcc -lm hello.c
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/c/TEMP/ccjLEGlU.o(.text+0x10):hello.c: multiple definition of `main'
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/usr/lib/libm.a(libcmain.o)(.text+0x0):libcmain.c: first defined here
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/usr/lib/libm.a(libcmain.o)(.text+0x6a):libcmain.c: undefined reference to `WinMain@16'
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collect2: ld returned 1 exit status
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</screen>
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<para>If you're using GCJ, you need to pass a "--main" flag:
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</para>
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<screen>
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gcj --main=Hello Hello.java
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</screen>
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</answer></qandaentry>
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<qandaentry id="faq.programming.win32-api">
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<question><para>How do I use Win32 API calls?</para></question>
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<answer>
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<para>Cygwin tools require that you explicitly link the import libraries
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for whatever Win32 API functions that you are going to use, with the exception
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of kernel32, which is linked automatically (because the startup and/or
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built-in code uses it).
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</para>
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<para>For example, to use graphics functions (GDI) you must link
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with gdi32 like this:
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</para>
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<para>gcc -o foo.exe foo.o bar.o -lgdi32
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</para>
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<para>or (compiling and linking in one step):
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</para>
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<para>gcc -o foo.exe foo.c bar.c -lgdi32
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</para>
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<para>The regular setup allows you to use the option -mwindows on the
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command line to include a set of the basic libraries (and also
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make your program a GUI program instead of a console program),
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including user32, gdi32 and, IIRC, comdlg32.
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</para>
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<para>It is a good idea to put import libraries last on your link line,
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or at least after all the object files and static libraries that reference them.
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</para>
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<note><para>There are a few restrictions for calls to the Win32 API.
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For details, see the User's Guide section
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<ulink url="http://cygwin.com/cygwin-ug-net/setup-env.html#setup-env-win32">Restricted Win32 environment</ulink>,
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as well as the User's Guide section
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<ulink url="http://cygwin.com/cygwin-ug-net/using.html#pathnames-win32-api">Using the Win32 file API in Cygwin applications</ulink>.</para></note>
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</answer></qandaentry>
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<qandaentry id="faq.programming.win32-no-cygwin">
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<question><para>How do I compile a Win32 executable that doesn't use Cygwin?</para></question>
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<answer>
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<para><emphasis role='bold'>(Please note: This section has not yet been updated for the latest net release.)</emphasis>
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</para>
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<para>The -mno-cygwin flag to gcc makes gcc link against standard Microsoft
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DLLs instead of Cygwin. This is desirable for native Windows programs
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that don't need a UNIX emulation layer.
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</para>
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<para>This is not to be confused with 'MinGW' (Minimalist GNU for Windows),
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which is a completely separate effort. That project's home page is
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<ulink url="http://www.mingw.org/index.shtml">http://www.mingw.org/index.shtml</ulink>.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.static-linking">
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<question><para>Can I build a Cygwin program that does not require cygwin1.dll at runtime?</para></question>
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<answer>
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<para>No. If your program uses the Cygwin API, then your executable cannot
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run without cygwin1.dll. In particular, it is not possible to
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statically link with a Cygwin library to obtain an independent,
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self-contained executable.
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</para>
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<para>If this is an issue because you intend to distribute your Cygwin
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application, then you had better read and understand
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<ulink url="http://cygwin.com/licensing.html">http://cygwin.com/licensing.html</ulink>, which explains the licensing
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options. Unless you purchase a special commercial license from Red
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Hat, then your Cygwin application must be Open Source.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.msvcrt-and-cygwin">
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<question><para>Can I link with both MSVCRT*.DLL and cygwin1.dll?</para></question>
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<answer>
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<para>No, you must use one or the other, they are mutually exclusive.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.no-console-window">
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<question><para>How do I make the console window go away?</para></question>
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<answer>
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<para>The default during compilation is to produce a console application.
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It you are writing a GUI program, you should either compile with
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-mwindows as explained above, or add the string
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"-Wl,--subsystem,windows" to the GCC command line.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.make-spaces">
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<question><para>Why does make complain about a "missing separator"?</para></question>
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<answer>
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<para>This problem usually occurs as a result of someone editing a Makefile
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with a text editor that replaces tab characters with spaces. Command
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lines must start with tabs. This is not specific to Cygwin.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.win32-headers">
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<question><para>Why can't we redistribute Microsoft's Win32 headers?</para></question>
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<answer>
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<para>Subsection 2.d.f of the `Microsoft Open Tools License agreement' looks
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like it says that one may not "permit further redistribution of the
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Redistributables to their end users". We take this to mean that we can
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give them to you, but you can't give them to anyone else, which is
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something that we can't agree to. Fortunately, we
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have our own Win32 headers which are pretty complete.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.msvs-mingw">
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<question><para>How do I use <literal>cygwin1.dll</literal> with Visual Studio or MinGW?</para></question>
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<answer>
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<para>Before you begin, note that Cygwin is licensed under the GNU GPL (as
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indeed are many other Cygwin-based libraries). That means that if your
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code links against the Cygwin dll (and if your program is calling
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functions from Cygwin, it must, as a matter of fact, be linked against
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it), you must apply the GPL to your source as well. Of course, this
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only matters if you plan to distribute your program in binary form. For
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more information, see <ulink url="http://gnu.org/licenses/gpl-faq.html">http://gnu.org/licenses/gpl-faq.html</ulink>. If
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that is not a problem, read on.
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</para>
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<para>If you want to load the DLL dynamically, read
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<literal>winsup/cygwin/how-cygtls-works.txt</literal> and the sample code in
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<literal>winsup/testsuite/cygload</literal> to understand how this works.
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The short version is:
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</para>
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<orderedlist><listitem><para>Make sure you have 4K of scratch space at the bottom of your stack.
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</para></listitem>
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<listitem><para>Invoke <literal>cygwin_dll_init()</literal>:
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<screen>
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HMODULE h = LoadLibrary("cygwin1.dll");
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void (*init)() = GetProcAddress(h, "cygwin_dll_init");
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init();
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</screen>
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</para></listitem>
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</orderedlist>
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<para>If you want to link statically from Visual Studio, to my knowledge
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none of the Cygwin developers have done this, but we have this report
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from the mailing list that it can be done this way:
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</para>
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<orderedlist><listitem><para>Use the impdef program to generate a .def file for the cygwin1.dll
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(if you build the cygwin dll from source, you will already have a def
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file)
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</para>
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<screen>
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impdef cygwin1.dll > cygwin1.def
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</screen>
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</listitem>
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<listitem><para>Use the MS VS linker (lib) to generate an import library
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</para>
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<screen>
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lib /def=cygwin1.def /out=cygwin1.lib
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</screen>
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</listitem>
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<listitem><para>Create a file "my_crt0.c" with the following contents
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</para>
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<screen>
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#include <sys/cygwin.h>
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#include <stdlib.h>
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typedef int (*MainFunc) (int argc, char *argv[], char **env);
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void
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my_crt0 (MainFunc f)
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{
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cygwin_crt0(f);
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}
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</screen>
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</listitem>
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<listitem><para>Use gcc in a Cygwin prompt to build my_crt0.c into a DLL
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(e.g. my_crt0.dll). Follow steps 1 and 2 to generate .def and
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.lib files for the DLL.
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</para>
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</listitem>
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<listitem><para>Download crt0.c from the cygwin website and include it in
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your sources. Modify it to call my_crt0() instead of
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cygwin_crt0().
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</para>
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</listitem>
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<listitem><para>Build your object files using the MS VC compiler cl.
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</para>
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</listitem>
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<listitem><para>Link your object files, cygwin1.lib, and my_crt0.lib (or
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whatever you called it) into the executable.
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</para></listitem>
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</orderedlist>
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<para>Note that if you are using any other Cygwin based libraries
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that you will probably need to build them as DLLs using gcc and
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then generate import libraries for the MS VC linker.
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</para>
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<para>Thanks to Alastair Growcott (alastair dot growcott at bakbone dot co
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dot uk) for this tip.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.linking-lib">
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<question><para>How do I link against a <literal>.lib</literal> file?</para></question>
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<answer>
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<para>If your <literal>.lib</literal> file is a normal static or import library with
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C-callable entry points, you can list <literal>foo.lib</literal> as an object file for
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gcc/g++, just like any <literal>*.o</literal> file. Otherwise, here are some steps:
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</para>
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<orderedlist><listitem><para>Build a C file with a function table. Put all functions you intend
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to use in that table. This forces the linker to include all the object
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files from the .lib. Maybe there is an option to force LINK.EXE to
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include an object file.
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</para></listitem>
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<listitem><para>Build a dummy 'LibMain'.
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</para></listitem>
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<listitem><para>Build a .def with all the exports you need.
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</para></listitem>
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<listitem><para>Link with your .lib using link.exe.
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</para></listitem>
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</orderedlist>
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<para>or
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</para>
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<orderedlist><listitem><para>Extract all the object files from the .lib using LIB.EXE.
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</para></listitem>
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<listitem><para>Build a dummy C file referencing all the functions you need, either
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with a direct call or through an initialized function pointer.
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</para></listitem>
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<listitem><para>Build a dummy LibMain.
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</para></listitem>
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<listitem><para>Link all the objects with this file+LibMain.
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</para></listitem>
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<listitem><para>Write a .def.
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</para></listitem>
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<listitem><para>Link.
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</para></listitem>
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</orderedlist>
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<para>You can use these methods to use MSVC (and many other runtime libs)
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with Cygwin development tools.
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</para>
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<para>Note that this is a lot of work (half a day or so), but much less than
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rewriting the runtime library in question from specs...
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</para>
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<para>Thanks to Jacob Navia (root at jacob dot remcomp dot fr) for this explanation.
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</para>
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</answer></qandaentry>
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<qandaentry id="faq.programming.building-cygwin">
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<question><para>How do I build Cygwin on my own?</para></question>
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<answer>
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<para>First, you need to make sure you have the necessary build tools
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installed; you at least need <literal>gcc</literal>, <literal>make</literal>,
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<literal>perl</literal>, and <literal>cocom</literal>. If you want to run
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the tests, <literal>dejagnu</literal> is also required.
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Normally, building ignores any errors in building the documentation,
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which requires the <literal>dblatex</literal>, <literal>docbook-xml45</literal>, <literal>docbook-xsl</literal>, and
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<literal>xmlto</literal> packages. For more information on building the
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documentation, see the README included in the <literal>cygwin-doc</literal> package.
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</para>
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|
|
<para>Next, get the Cygwin source. Ideally, you should check out
|
|
what you need from CVS (<ulink url="http://cygwin.com/cvs.html" />). This is the
|
|
<emphasis>preferred method</emphasis> for acquiring the sources. Otherwise, if
|
|
you are trying to duplicate a cygwin release then you should
|
|
download the corresponding source package
|
|
(<literal>cygwin-x.y.z-n-src.tar.bz2</literal>). </para>
|
|
|
|
<para>You <emphasis>must</emphasis> build cygwin in a separate directory from
|
|
the source, so create something like a <literal>build/</literal> directory.
|
|
Assuming you checked out the source in <literal>/oss/src/</literal>, and you
|
|
also want to install to the temporary location <literal>install</literal>:
|
|
</para>
|
|
<screen>
|
|
mkdir /oss/build
|
|
mkdir /oss/install
|
|
cd build
|
|
(/oss/src/configure --prefix=/oss/install -v; make) >& make.out
|
|
make install > install.log 2>&1
|
|
</screen>
|
|
|
|
<para>To check a cygwin1.dll, run "make check" in the build/i?86*cygwin/winsup
|
|
directory created after running make above.
|
|
If that works, install everything <emphasis>except</emphasis> the dll (if
|
|
you can). Then, close down all cygwin programs (including bash windows,
|
|
inetd, etc.), save your old dll, and copy the new dll to the correct
|
|
place. Then start up a bash window, or run a cygwin program from the
|
|
Windows command prompt, and see what happens.
|
|
</para>
|
|
<para>If you get the error "shared region is corrupted" it means that two
|
|
different versions of cygwin1.dll are running on your machine at the
|
|
same time. Remove all but one.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.debugging-cygwin">
|
|
<question><para>I may have found a bug in Cygwin, how can I debug it (the symbols in gdb look funny)?</para></question>
|
|
<answer>
|
|
|
|
<para>Debugging symbols are stripped from distibuted Cygwin binaries, so any
|
|
symbols that you see in gdb are basically meaningless. It is also a good
|
|
idea to use the latest code in case the bug has been fixed, so we
|
|
recommend trying the latest snapshot from
|
|
<ulink url="http://cygwin.com/snapshots/" /> or building the DLL from CVS.
|
|
</para>
|
|
<para>To build a debugging version of the Cygwin DLL, you will need to follow
|
|
the instructions at <ulink url="http://cygwin.com/faq/faq-nochunks.html#faq.programming.building-cygwin" />.
|
|
You can also contact the mailing list for pointers (a simple test case that
|
|
demonstrates the bug is always welcome).
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.compiling-unsupported">
|
|
<question><para>How can I compile Cygwin for an unsupported platform (PowerPC, Alpha, ARM, Itanium)?</para></question>
|
|
<answer>
|
|
|
|
<para>Unfortunately, this will be difficult. Exception handling and signals
|
|
support semantics and args have been designed for x86 so you would need
|
|
to write specific support for your platform. We don't know of any other
|
|
incompatibilities. Please send us patches if you do this work!
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.adjusting-heap">
|
|
<question><para>How can I adjust the heap/stack size of an application?</para></question>
|
|
<answer>
|
|
|
|
<para>If you need to change the maximum amount of memory available to Cygwin, see
|
|
<ulink url="http://cygwin.com/cygwin-ug-net/setup-maxmem.html">http://cygwin.com/cygwin-ug-net/setup-maxmem.html</ulink>. Otherwise,
|
|
just pass heap/stack linker arguments to gcc. To create foo.exe with
|
|
a heap size of 200MB and a stack size of 8MB, you would invoke
|
|
gcc as:
|
|
</para>
|
|
<para><literal>gcc -Wl,--heap,200000000,--stack,8000000 -o foo foo.c</literal>
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.dll-cygcheck">
|
|
<question><para>How can I find out which DLLs are needed by an executable?</para></question>
|
|
<answer>
|
|
|
|
<para><literal>objdump -p</literal> provides this information, but is rather verbose.
|
|
</para>
|
|
<para><literal>cygcheck</literal> will do this much more concisely, and operates
|
|
recursively, provided the command is in your path.
|
|
</para>
|
|
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.dll-building">
|
|
<question><para>How do I build a DLL?</para></question>
|
|
<answer>
|
|
|
|
<para>There's documentation that explains the process in the Cygwin User's
|
|
Guide here: <ulink url="http://cygwin.com/cygwin-ug-net/dll.html">http://cygwin.com/cygwin-ug-net/dll.html</ulink>
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.breakpoint">
|
|
<question><para>How can I set a breakpoint at MainCRTStartup?</para></question>
|
|
<answer>
|
|
|
|
<para><emphasis role='bold'>(Please note: This section has not yet been updated for the latest net release.)</emphasis>
|
|
</para>
|
|
<para>Set a breakpoint at *0x401000 in gdb and then run the program in
|
|
question.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.dll-relocatable">
|
|
<question><para>How can I build a relocatable dll?</para></question>
|
|
<answer>
|
|
|
|
<para><emphasis role='bold'>(Please note: This section has not yet been updated for the latest net release. However, there was a discussion on the cygwin mailing list once that addresses this issue. Read <ulink url="http://cygwin.com/ml/cygwin/2000-06/msg00688.html">http://cygwin.com/ml/cygwin/2000-06/msg00688.html</ulink> and related messages.)</emphasis>
|
|
</para>
|
|
<para>You must execute the following sequence of five commands, in this
|
|
order:
|
|
</para>
|
|
<screen>
|
|
$(LD) -s --base-file BASEFILE --dll -o DLLNAME OBJS LIBS -e ENTRY
|
|
|
|
$(DLLTOOL) --as=$(AS) --dllname DLLNAME --def DEFFILE \
|
|
--base-file BASEFILE --output-exp EXPFILE
|
|
|
|
$(LD) -s --base-file BASEFILE EXPFILE -dll -o DLLNAME OBJS LIBS -e ENTRY
|
|
|
|
$(DLLTOOL) --as=$(AS) --dllname DLLNAME --def DEFFILE \
|
|
--base-file BASEFILE --output-exp EXPFILE
|
|
|
|
$(LD) EXPFILE --dll -o DLLNAME OBJS LIBS -e ENTRY
|
|
</screen>
|
|
|
|
<para>In this example, $(LD) is the linker, ld.
|
|
</para>
|
|
<para>$(DLLTOOL) is dlltool.
|
|
</para>
|
|
<para>$(AS) is the assembler, as.
|
|
</para>
|
|
<para>DLLNAME is the name of the DLL you want to create, e.g., tcl80.dll.
|
|
</para>
|
|
<para>OBJS is the list of object files you want to put into the DLL.
|
|
</para>
|
|
<para>LIBS is the list of libraries you want to link the DLL against. For
|
|
example, you may or may not want -lcygwin. You may want -lkernel32.
|
|
Tcl links against -lcygwin -ladvapi32 -luser32 -lgdi32 -lcomdlg32
|
|
-lkernel32.
|
|
</para>
|
|
<para>DEFFILE is the name of your definitions file. A simple DEFFILE would
|
|
consist of ``EXPORTS'' followed by a list of all symbols which should
|
|
be exported from the DLL. Each symbol should be on a line by itself.
|
|
Other programs will only be able to access the listed symbols.
|
|
</para>
|
|
<para>BASEFILE is a temporary file that is used during this five stage
|
|
process, e.g., tcl.base.
|
|
</para>
|
|
<para>EXPFILE is another temporary file, e.g., tcl.exp.
|
|
</para>
|
|
<para>ENTRY is the name of the function which you want to use as the entry
|
|
point. This function should be defined using the WINAPI attribute,
|
|
and should take three arguments:
|
|
int WINAPI startup (HINSTANCE, DWORD, LPVOID)
|
|
</para>
|
|
<para>This means that the actual symbol name will have an appended @12, so if
|
|
your entry point really is named <literal>startup</literal>, the string you should
|
|
use for ENTRY in the above examples would be <literal>startup@12</literal>.
|
|
</para>
|
|
<para>If your DLL calls any Cygwin API functions, the entry function will need
|
|
to initialize the Cygwin impure pointer. You can do that by declaring
|
|
a global variable <literal>_impure_ptr</literal>, and then initializing it in the
|
|
entry function. Be careful not to export the global variable
|
|
<literal>_impure_ptr</literal> from your DLL; that is, do not put it in DEFFILE.
|
|
</para>
|
|
<screen>
|
|
/* This is a global variable. */
|
|
struct _reent *_impure_ptr;
|
|
extern struct _reent *__imp_reent_data;
|
|
|
|
int entry (HINSTANT hinst, DWORD reason, LPVOID reserved)
|
|
{
|
|
_impure_ptr = __imp_reent_data;
|
|
/* Whatever else you want to do. */
|
|
}
|
|
</screen>
|
|
|
|
<para>You may put an optional `--subsystem windows' on the $(LD) lines. The
|
|
Tcl build does this, but I admit that I no longer remember whether
|
|
this is important. Note that if you specify a --subsytem <x> flag to ld,
|
|
the -e entry must come after the subsystem flag, since the subsystem flag
|
|
sets a different default entry point.
|
|
</para>
|
|
<para>You may put an optional `--image-base BASEADDR' on the $(LD) lines.
|
|
This will set the default image base. Programs using this DLL will
|
|
start up a bit faster if each DLL occupies a different portion of the
|
|
address space. Each DLL starts at the image base, and continues for
|
|
whatever size it occupies.
|
|
</para>
|
|
<para>Now that you've built your DLL, you may want to build a library so
|
|
that other programs can link against it. This is not required: you
|
|
could always use the DLL via LoadLibrary. However, if you want to be
|
|
able to link directly against the DLL, you need to create a library.
|
|
Do that like this:
|
|
</para>
|
|
<para>$(DLLTOOL) --as=$(AS) --dllname DLLNAME --def DEFFILE --output-lib LIBFILE
|
|
</para>
|
|
<para>$(DLLTOOL), $(AS), DLLNAME, and DEFFILE are the same as above. Make
|
|
sure you use the same DLLNAME and DEFFILE, or things won't work right.
|
|
</para>
|
|
<para>LIBFILE is the name of the library you want to create, e.g.,
|
|
libtcl80.a. You can then link against that library using something
|
|
like -ltcl80 in your linker command.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.debug">
|
|
<question><para>How can I debug what's going on?</para></question>
|
|
<answer>
|
|
|
|
<para>You can debug your application using <literal>gdb</literal>. Make sure you
|
|
compile it with the -g flag! If your application calls functions in
|
|
MS DLLs, gdb will complain about not being able to load debug information
|
|
for them when you run your program. This is normal since these DLLs
|
|
don't contain debugging information (and even if they did, that debug
|
|
info would not be compatible with gdb).
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.system-trace">
|
|
<question><para>Can I use a system trace mechanism instead?</para></question>
|
|
<answer>
|
|
|
|
<para>Yes. You can use the <literal>strace.exe</literal> utility to run other cygwin
|
|
programs with various debug and trace messages enabled. For information
|
|
on using <literal>strace</literal>, see the Cygwin User's Guide or the file
|
|
<literal>winsup/utils/utils.sgml</literal> in the Cygwin sources.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.gdb-signals">
|
|
<question><para>Why doesn't gdb handle signals?</para></question>
|
|
<answer>
|
|
|
|
<para>Unfortunately, there is only minimal signal handling support in gdb
|
|
currently. Signal handling only works with Windows-type signals.
|
|
SIGINT may work, SIGFPE may work, SIGSEGV definitely does. You cannot
|
|
'stop', 'print' or 'nopass' signals like SIGUSR1 or SIGHUP to the
|
|
process being debugged.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.linker">
|
|
<question><para>The linker complains that it can't find something.</para></question>
|
|
<answer>
|
|
|
|
<para>A common error is to put the library on the command line before
|
|
the thing that needs things from it.
|
|
</para>
|
|
<para>This is wrong <literal>gcc -lstdc++ hello.cc</literal>.
|
|
This is right <literal>gcc hello.cc -lstdc++</literal>.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.stat64">
|
|
<question><para>Why do I get an error using <literal>struct stat64</literal>?</para></question>
|
|
<answer>
|
|
|
|
<para><literal>struct stat64</literal> is not used in Cygwin, just
|
|
use <literal>struct stat</literal>. It's 64 bit aware.</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.undeclared-functions">
|
|
<question><para>I use a function I know is in the API, but I still get a link error.</para></question>
|
|
<answer>
|
|
|
|
<para>The function probably isn't declared in the header files, or
|
|
the UNICODE stuff for it isn't filled in.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.libc">
|
|
<question><para>Can you make DLLs that are linked against libc ?</para></question>
|
|
<answer>
|
|
|
|
<para>Yes.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.malloc-h">
|
|
<question><para>Where is malloc.h?</para></question>
|
|
<answer>
|
|
|
|
<para>It exists, but you should rather include stdlib.h instead of malloc.h.
|
|
stdlib.h is POSIX standard for defining malloc and friends, malloc.h is
|
|
definitely non-standard.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.own-malloc">
|
|
<question><para>Can I use my own malloc?</para></question>
|
|
<answer>
|
|
|
|
<para>If you define a function called <literal>malloc</literal> in your own code, and link
|
|
with the DLL, the DLL <emphasis>will</emphasis> call your <literal>malloc</literal>. Needless to
|
|
say, you will run into serious problems if your malloc is buggy.
|
|
</para>
|
|
<para>If you run any programs from the DOS command prompt, rather than from in
|
|
bash, the DLL will try and expand the wildcards on the command line.
|
|
This process uses <literal>malloc</literal> <emphasis>before</emphasis> your main line is started.
|
|
If you have written your own <literal>malloc</literal> to need some initialization
|
|
to occur after <literal>main</literal> is called, then this will surely break.
|
|
</para>
|
|
<para>Moreover, there is an outstanding issue with <literal>_malloc_r</literal> in
|
|
<literal>newlib</literal>. This re-entrant version of <literal>malloc</literal> will be called
|
|
directly from within <literal>newlib</literal>, by-passing your custom version, and
|
|
is probably incompatible with it. But it may not be possible to replace
|
|
<literal>_malloc_r</literal> too, because <literal>cygwin1.dll</literal> does not export it and
|
|
Cygwin does not expect your program to replace it. This is really a
|
|
newlib issue, but we are open to suggestions on how to deal with it.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.msvc-gcc-objects">
|
|
<question><para>Can I mix objects compiled with msvc++ and gcc?</para></question>
|
|
<answer>
|
|
|
|
<para>Yes, but only if you are combining C object files. MSVC C++ uses a
|
|
different mangling scheme than GNU C++, so you will have difficulties
|
|
combining C++ objects.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.gdb-msvc">
|
|
<question><para>Can I use the gdb debugger to debug programs built by VC++?</para></question>
|
|
<answer>
|
|
|
|
<para>No, not for full (high level source language) debugging.
|
|
The Microsoft compilers generate a different type of debugging
|
|
symbol information, which gdb does not understand.
|
|
</para>
|
|
<para>However, the low-level (assembly-type) symbols generated by
|
|
Microsoft compilers are coff, which gdb DOES understand.
|
|
Therefore you should at least be able to see all of your
|
|
global symbols; you just won't have any information about
|
|
data types, line numbers, local variables etc.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.x86-assembly">
|
|
<question><para>Where can I find info on x86 assembly?</para></question>
|
|
<answer>
|
|
|
|
<para>CPU reference manuals for Intel's current chips are available in
|
|
downloadable PDF form on Intel's web site:
|
|
</para>
|
|
<para><ulink url="http://developer.intel.com/">http://developer.intel.com/</ulink>
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.make-scripts">
|
|
<question><para>Shell scripts aren't running properly from my makefiles?</para></question>
|
|
<answer>
|
|
|
|
<para>If your scripts are in the current directory, you must have <literal>.</literal>
|
|
(dot) in your $PATH. (It is not normally there by default.) Better yet,
|
|
add /bin/sh in front of each and every shell script invoked in your Makefiles.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.preprocessor">
|
|
<question><para>What preprocessor macros do I need to know about?</para></question>
|
|
<answer>
|
|
|
|
<para>gcc for Cygwin defines __CYGWIN__ when building for a Cygwin
|
|
environment.
|
|
</para>
|
|
<para>Microsoft defines the preprocessor symbol _WIN32 in their Windows
|
|
development environment.
|
|
</para>
|
|
<para>In gcc for Cygwin, _WIN32 is only defined when you use the -mwin32
|
|
gcc command line options. This is because Cygwin is supposed to be a
|
|
POSIX emulation environment in the first place and defining _WIN32 confuses
|
|
some programs which think that they have to make special concessions for
|
|
a Windows environment which Cygwin handles automatically.
|
|
</para>
|
|
<para>Check out the predefined symbols in detail by running, for example
|
|
</para>
|
|
<screen>
|
|
$ gcc -dM -E -xc /dev/null >gcc.txt
|
|
$ gcc -mwin32 -dM -E -xc /dev/null >gcc-mwin32.txt
|
|
</screen>
|
|
<para>Then use the diff and grep utilities to check what the difference is.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.unix-gui">
|
|
<question><para>How should I port my Unix GUI to Windows?</para></question>
|
|
<answer>
|
|
|
|
<para>There are two basic strategies for porting Unix GUIs to Windows.
|
|
</para>
|
|
<para>The first is to use a portable graphics library such as tcl/tk, X11, or
|
|
V (and others?). Typically, you will end up with a GUI on Windows that
|
|
requires some runtime support. With tcl/tk, you'll want to include the
|
|
necessary library files and the tcl/tk DLLs. In the case of X11, you'll
|
|
need everyone using your program to have the X11 server installed.
|
|
</para>
|
|
<para>The second method is to rewrite your GUI using Win32 API calls (or MFC
|
|
with VC++). If your program is written in a fairly modular fashion, you
|
|
may still want to use Cygwin if your program contains a lot of shared
|
|
(non-GUI-related) code. That way you still gain some of the portability
|
|
advantages inherent in using Cygwin.
|
|
</para>
|
|
</answer></qandaentry>
|
|
|
|
<qandaentry id="faq.programming.djgpp">
|
|
<question><para>Why not use DJGPP ?</para></question>
|
|
<answer>
|
|
|
|
<para>DJGPP is a similar idea, but for DOS instead of Win32. DJGPP uses a
|
|
"DOS extender" to provide a more reasonable operating interface for its
|
|
applications. The Cygwin toolset doesn't have to do this since all of
|
|
the applications are native WIN32. Applications compiled with the
|
|
Cygwin tools can access the Win32 API functions, so you can write
|
|
programs which use the Windows GUI.
|
|
</para>
|
|
<para>You can get more info on DJGPP by following
|
|
<ulink url="http://www.delorie.com/">http://www.delorie.com/</ulink>.
|
|
</para></answer></qandaentry>
|
|
|