Default GCC compiler options and how to change them

[Hamish McIntyre-Bhatty]

On 08/05/2025 20:59, Brian Inglis via Cygwin wrote:
> On 2025-05-08 13:25, Hamish McIntyre-Bhatty via Cygwin wrote:
>> I've run into a blocker when trying to build wxPython that wasn't a 
>> problem when I last did it (which amittedly was over a year ago). Some 
>> -werror flags are being passed to GCC, but I can't see where they're 
>> coming from. Are there any defaults set for GCC that mean -werror 
>> might be turned on?
>>
>> When I build wxPython on my host (Linux) system, I don't get the same 
>> issues, so I'm assuming there are defaults being set somewhere. If 
>> anyone could offer some help I'd be very appreciative.
> 
> Try gcc -v and gcc -###:
> 
> $ gcc -v
> Using built-in specs.
> COLLECT_GCC=/usr/bin/gcc
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-cygwin/12/lto-wrapper.exe
> Target: x86_64-pc-cygwin
> Configured with: /mnt/share/cygpkgs/gcc/gcc.x86_64/src/gcc-12.4.0/ 
> configure --srcdir=/mnt/share/cygpkgs/gcc/gcc.x86_64/src/gcc-12.4.0 -- 
> prefix=/usr --exec-prefix=/usr --localstatedir=/var --sysconfdir=/etc -- 
> docdir=/usr/share/doc/gcc --htmldir=/usr/share/doc/gcc/html -C -- 
> build=x86_64-pc-cygwin --host=x86_64-pc-cygwin --target=x86_64-pc-cygwin 
> --without-libiconv-prefix --without-libintl-prefix --libexecdir=/usr/lib 
> --with-gcc-major-version-only --enable-shared --enable-shared-libgcc -- 
> enable-static --enable-version-specific-runtime-libs --enable-bootstrap 
> --enable-__cxa_atexit --enable-clocale=newlib --with-dwarf2 --with- 
> tune=generic --enable-languages=ada,c,c++,fortran,lto,objc,obj-c++,jit 
> --enable-graphite --enable-threads=posix --enable-libatomic --enable- 
> libgomp --enable-libquadmath --enable-libquadmath-support --disable- 
> libssp --enable-libada --disable-symvers --disable-multilib --with-gnu- 
> ld --with-gnu-as --with-cloog-include=/usr/include/cloog-isl --without- 
> libiconv-prefix --without-libintl-prefix --with-system-zlib --enable- 
> linker-build-id --with-default-libstdcxx-abi=gcc4-compatible --enable- 
> libstdcxx-filesystem-ts
> Thread model: posix
> Supported LTO compression algorithms: zlib zstd
> gcc version 12.4.0 (GCC)
> 
> $ gcc -###
> Using built-in specs.
> COLLECT_GCC=/usr/bin/gcc
> COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-cygwin/12/lto-wrapper.exe
> Target: x86_64-pc-cygwin
> Configured with: /mnt/share/cygpkgs/gcc/gcc.x86_64/src/gcc-12.4.0/ 
> configure --srcdir=/mnt/share/cygpkgs/gcc/gcc.x86_64/src/gcc-12.4.0 -- 
> prefix=/usr --exec-prefix=/usr --localstatedir=/var --sysconfdir=/etc -- 
> docdir=/usr/share/doc/gcc --htmldir=/usr/share/doc/gcc/html -C -- 
> build=x86_64-pc-cygwin --host=x86_64-pc-cygwin --target=x86_64-pc-cygwin 
> --without-libiconv-prefix --without-libintl-prefix --libexecdir=/usr/lib 
> --with-gcc-major-version-only --enable-shared --enable-shared-libgcc -- 
> enable-static --enable-version-specific-runtime-libs --enable-bootstrap 
> --enable-__cxa_atexit --enable-clocale=newlib --with-dwarf2 --with- 
> tune=generic --enable-languages=ada,c,c++,fortran,lto,objc,obj-c++,jit 
> --enable-graphite --enable-threads=posix --enable-libatomic --enable- 
> libgomp --enable-libquadmath --enable-libquadmath-support --disable- 
> libssp --enable-libada --disable-symvers --disable-multilib --with-gnu- 
> ld --with-gnu-as --with-cloog-include=/usr/include/cloog-isl --without- 
> libiconv-prefix --without-libintl-prefix --with-system-zlib --enable- 
> linker-build-id --with-default-libstdcxx-abi=gcc4-compatible --enable- 
> libstdcxx-filesystem-ts
> Thread model: posix
> Supported LTO compression algorithms: zlib zstd
> gcc version 12.4.0 (GCC)
> 

Thanks for the reply, but that doesn't seem to be quite what I'm looking 
for, unless I missed something in the output on your Cygwin install. 
Perhaps I need to look in the spec files mentioned in the output?

Re the gold stars thing, I reckon you deserve one too, you always seem 
to be popping in with helpful answers to queries.

Best,
Hamish