Cygwin: autoload: introduce LoadDLLfunc_pfx_only

This macro loads and defines a function just as usual, except
that the Windows function is exposed only with the prefix
_win32_.  So Windows select (the immediate victim) is only
exposed as _win32_select.  That allows to autoload the windows
function without collision with a Cygwin function of the same
name.

For a start, only define the most simple macro, setting all
extensions to 0.


Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/autoload.cc

@@ -123,6 +123,33 @@ _win32_" #name ":					\n\
   .asciz	\"" #name "\"				\n\
   .text							\n\
 ");
+
+/* Do not export function "foo" as "foo". Only export it as "_win32_foo".
+   That allows to autoload and use a Windows function having the same name
+   as a Cygwin function. Namely select. */
+#define LoadDLLfunc_pfx_only(name, dllname) \
+  LoadDLLprime (dllname, dll_func_load, 0) \
+  __asm__ ("						\n\
+  .section	." #dllname "_autoload_text,\"wx\"	\n\
+  .global	_win32_" #name "			\n\
+  .align	16					\n\
+_win32_" #name ":					\n\
+  movq		3f(%rip),%rax				\n\
+  jmp		*%rax					\n\
+1:movq		2f(%rip),%rax				\n\
+  push		%rbp		# Keep 16 byte aligned	\n\
+  push		%r9					\n\
+  push		%r8					\n\
+  push		%rdx					\n\
+  push		%rcx					\n\
+  call		*(%rax)					\n\
+2:.quad		." #dllname "_info			\n\
+  .hword	0					\n\
+  .hword	0					\n\
+3:.quad		1b					\n\
+  .asciz	\"" #name "\"				\n\
+  .text							\n\
+");
 #else
 #error unimplemented for this target
 #endif