use new gcc warnings

[bagder]

Continued work on @cooljeanius' take from #2307 with my added polish to make sure they build fine all over.

[cooljeanius]

Thank you!

[MarcelRaad]

Now I get:

http.c: In function 'Curl_copy_header_value':
http.c:220:9: error: potential null pointer dereference [-Werror=null-dereference]
   while(*header && (*header != ':'))

We aren't annotating parameters as nonnull, are we?

[bagder]

We aren't annotating parameters as nonnull, are we?

No... it rather makes me suspect it uses the assert() above as a hint, but I'm a bit puzzled. This function really is not possible to call with a NULL pointer in the current code, I checked all the current call paths.

[bagder]

btw, which compiler (version) gives you that warning?

[MarcelRaad]

This is MinGW-w64's GCC 7.3:

Target: i686-w64-mingw32
Configured with: ../gcc-7.3.0/configure --prefix=/mingw32 --with-local-prefix=/mingw32/local --build=i686-w64-mingw32 --host=i686-w64-mingw32 --target=i686-w64-mingw32 --with-native-system-header-dir=/mingw32/i686-w64-mingw32/include --libexecdir=/mingw32/lib --enable-bootstrap --with-arch=i686 --with-tune=generic --enable-languages=c,lto,c++,objc,obj-c++,fortran,ada --enable-shared --enable-static --enable-libatomic --enable-threads=posix --enable-graphite --enable-fully-dynamic-string --enable-libstdcxx-time=yes --enable-libstdcxx-filesystem-ts=yes --disable-libstdcxx-pch --disable-libstdcxx-debug --disable-isl-version-check --enable-lto --enable-libgomp --disable-multilib --enable-checking=release --disable-rpath --disable-win32-registry --disable-nls --disable-werror --disable-symvers --with-libiconv --with-system-zlib --with-gmp=/mingw32 --with-mpfr=/mingw32 --with-mpc=/mingw32 --with-isl=/mingw32 --with-pkgversion='Rev1, Built by MSYS2 project' --with-bugurl=https://sourceforge.net/projects/msys2 --with-gnu-as --with-gnu-ld --disable-sjlj-exceptions --with-dwarf2
Thread model: posix
gcc version 7.3.0 (Rev1, Built by MSYS2 project)

[bagder]

Interestingly, I don't get that error with gcc 7.3.0 on Linux (7.3.0-15 on debian).

[bagder]

@MarcelRaad: does the warning go away if you remove the assert? Or do you need to add a "real" check for NULL there to make it go away?

[MarcelRaad]

Yes, removing the assert makes the warning go away! And there's also one in curlx_strtoofft that goes away after removing the assert.

[bagder]

Ah, will you land removals of those asserts then? I don't think those are terribly valuable anyway since if we do get NULL pointers there we will crash/trigger valgrind reports etc.

[MarcelRaad]

OK, will do!