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GCC: problem with library search path when targeting mingw


hello,

I'm a big fan of cygwin and I use it a lot to compile mingw apps,
however with the latest mingw-runtime, I'm having trouble running
configure scripts successfully as test such 'dlopen() in -ldl', which
used to fail for mingw target (as expected) now succeeds. This causes
havoc in compilation as the resulting config.h file contains reference
to APIs not supported by mingw.

after having a look at gcc -mno-cygwin -print-search-dirs, I think I may
have found the culprit in the following element of the library search path:
'/usr/lib/gcc/i686-pc-mingw/3.4.4/../../..', as this points back
straight at /usr/lib, the cygin main library path. This means now that
the following command

$ gcc -mno-cygwin dlopen-test.c -dl

Now passes with flying colors. I have to edit all my config.h as I do
not know of any way to remove this path from the search paths

Similarily, I have a similar but less serious problems with headers
paths for files such as math.h, float.h, these are available for both
cygwin and mingw, but they are different files.Unfortunately,
"/usr/lib/gcc/i686-pc-cygwin/3.4.4/include" has precedence over
'/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../i686-pc-mingw32/include'
when targetting mingw by default, therefore the cygwin version is chosen
over the mingw one.
In 99% of cases, this is usually not a problem, as the files are nearly
identical, but they are some Microsoft specific code in the mingw, which
is required to compile Trolltech QT, for example.
If i use the following compiler option '-isystem /usr/include/mingw',
then everything works fine.

I hope this help
  Damien

--------

For reference:

binutils-20060709-1
gcc-3.4.4-1
mingw-runtime-3.10.1

$ gcc -mno-cygwin -print-search-dirs
install: /usr/lib/gcc/i686-pc-mingw32/3.4.4/
programs:
=/usr/lib/gcc/i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/:/usr/libexec/gcc/i686-pc-mingw32/3.4.4/:/usr/libexec/gcc/i686-pc-mingw32/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../i686-pc-mingw32/bin/i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../i686-pc-mingw32/bin/
libraries:
=/usr/lib/gcc/i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../i686-pc-mingw32/lib/i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../i686-pc-mingw32/lib/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../i686-pc-mingw32/3.4.4/:/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../:/lib/i686-pc-mingw32/3.4.4/:/lib/:/usr/lib/i686-pc-mingw32/3.4.4/:/usr/lib/

$ gcc -print-search-dirs
install: /usr/lib/gcc/i686-pc-cygwin/3.4.4/
programs:
=/usr/lib/gcc/i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/:/usr/libexec/gcc/i686-pc-cygwin/3.4.4/:/usr/libexec/gcc/i686-pc-cygwin/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/bin/i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/bin/
libraries:
=/usr/lib/gcc/i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/lib/i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/lib/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../i686-pc-cygwin/3.4.4/:/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../:/lib/i686-pc-cygwin/3.4.4/:/lib/:/usr/lib/i686-pc-cygwin/3.4.4/:/usr/lib/

$ cpp -mno-cygwin --verbose test.c
Reading specs from /usr/lib/gcc/i686-pc-mingw32/3.4.4/specs
Configured with: /gcc/gcc-3.4.4/gcc-3.4.4-1/configure --verbose
--prefix=/usr --exec-prefix=/usr --sysconfdir=/etc --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--enable-languages=c,ada,c++,d,f77,java,objc --enable-nls
--without-included-gettext --enable-version-specific-runtime-libs
--without-x --enable-libgcj --disable-java-awt --with-system-zlib
--enable-interpreter --disable-libgcj-debug --enable-threads=posix
--enable-java-gc=boehm --disable-win32-registry --enable-sjlj-exceptions
--enable-hash-synchronization --enable-libstdcxx-debug : (reconfigured)
Thread model: posix
gcc version 3.4.4 (cygming special) (gdc 0.12, using dmd 0.125)
/usr/lib/gcc/i686-pc-mingw32/3.4.4/cc1.exe -E -quiet -v -D__MSVCRT__
-D__MINGW32__ -DWIN32 -D_WIN32 -D__WIN32 -D__WIN32__ -DWINNT -idirafter
/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../include/w32api -idirafter
/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../i686-pc-mingw32/lib/../../include/w32api


test.c -mno-cygwin -mtune=pentiumpro
ignoring nonexistent directory "/usr/local/include/mingw"
ignoring duplicate directory "/usr/include/mingw"
ignoring duplicate directory
"/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../i686-pc-mingw32/lib/../../include/w32api"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include
/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../i686-pc-mingw32/include
/usr/lib/gcc/i686-pc-mingw32/3.4.4/../../../../include/w32api
End of search list.
# 1 "test.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "test.c"
# 1 "/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/float.h" 1 3 4
# 2 "test.c" 2

int main(int argc, char **argv) {
   return 0;
}




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