86 lines
3.0 KiB
Plaintext
86 lines
3.0 KiB
Plaintext
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This code is a utility function I was considering adding to Mingw32. The
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Microsoft versions of argc, argv construction use quotes and backslashes
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to allow the user to pass arguments containing spaces (or quotes) to
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programs they invoke. The rules are
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- Arguments containing spaces must be enclosed in quotes.
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- A quote can be passed by preceeding it with a backslash.
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- Backslashes immediately preceeding a quote must be doubled to avoid
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escaping the quote.
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Thus an argument like:
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-D="Foo Bar\\"
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needs to be mangled as:
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"-D\"Foo Bar\\\\\""
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in order to get to the program as what was intended above.
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The fix_argv set of functions is meant to be used with spawnv and the
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like to allow a program to set up an argv array for the spawned program
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and have that array duplicated *exactly* in the spawned program, no
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matter what it contains (it also quotes 'globbing' characters like *
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and ?, so it does not matter if the destination has globbing turned on
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or not; it might be a reasonable extension to allow a flag to allow
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globbing characters to pass through unmolested, but they would still
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be quoted if the string contained whitespace).
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The reason for writing this came up because of problems with arguments
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like -DBLAH="Foo Bar" to GCC (define BLAH as a preprocessor constant
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being the string "Foo Bar", including the quotes). Because GCC simply
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passes the argument directly to CPP (the preprocessor) it had to be
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escaped *twice*:
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"-DBLAH=\"\\\"Foo Bar\\\"\""
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This would reach GCC as
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-DBLAH="\"Foo Bar\""
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And that would reach CPP as the desired
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-DBLAH="Foo Bar"
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One level of quoting and escaping is to be expected (although MS's
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standard is, arguably, not very good), but forcing the user to know
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how many different programs the argument is going to pass through,
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and perform double quoting and escaping, seems unreasonable. If
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GCC and friends all used fix_argv (they use their own version of
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it now) then the original argument could be
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"-DBLAH=\"Foo Bar\""
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And that would work fine, no matter how many different tools it
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passed through.
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The only basic limitation with this code is that it assumes that all
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the spawned programs use Microsoft-type escaping when interpreting
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their command line. Most programs on Win32 machines do (anything
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compiled with Mingw32 will).
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For now, this code has been relegated to 'sample' status. If you want
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to use it, feel free (it is public domain after all).
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Colin.
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P.S. Just out of interest you might try writing your own little program
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to look at the interaction of wildcards and quotes. Use the glob.exe
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program in ../globbing and see what it does with
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glob "foo*.txt"
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even if there are files foo.txt and foobar.txt in the same directory.
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Note that
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del "My *.txt"
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works (i.e. it deletes all files starting with My<space>). This could
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not be done unless del does globbing *after* processing escapes and
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quotes, which is not the way it seems to work normally (again see
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the glob example).
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