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Re: GCC: problem with library search path when targeting mingw

I'm not sure that I agree with your assements, /usr/lib as always been available (at least displayed) as a default search path in 'print-search-dirs' even when using the -mno-cygwin switch, but for some reason, has always been ignored when linking for MinGW.

I think the problem has to do with '/usr/lib/gcc/i686-pc-mingw/3.4.4/../../..' in the search paths, I'm not sure if this path was available in the previous packages of gcc/mingw-runtime/binutils (I don't feel like downgrading to check it out :) ), but this is the one that's giving me trouble rather than /usr/lib, so I don't think -Wl,-nostdlib will be of any help.

I agree with you that -mno-cygwin has been a bad choice, as it requires a lot of hacking around to get some configure scripts to recognize/use this option when cross-compiling autotools based packages for MinGW, but until this recent problem, I've always managed to get by without tweaking configure scripts, typically overriding CC, CXX, CPPFLAGS, etc... on the command line was enough.

Damien

Christopher Faylor wrote:

 Thanks for the report.  This has been mentioned before, it's a problem in
gcc's 'specs', which are command-line pattern matching strings (more-or-less)
used by the gcc compiler driver to select the right options for the
sub-programs that it invokes.  It's basically a consequence of the fact that
we're using the same driver to drive a native compiler /and/ a cross-compiler;
normally, a cross-compiler wouldn't include any of the system paths such as
/usr/lib at all, but for a native compiler that's exactly what you want it to
do.


The /usr/lib inclusion is actually likely to be a binutils "problem"
since ld includes /usr/lib by default.  Possibly adding -Wl,-nostdlib to
the command line would help.

In any event, I really think that -mno-cygwin is 1) a bad choice for an
option name and 2) a bad way to accomplish what is essentially
cross-compilation.  I regret that I stood by idly and watched that
option go into gcc.

cgf



Damien Fouilleul wrote:
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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