CMake ignoring compilation flags [duplicate] - c++

Question

This question already has answers here:
Passing compiler options in CMake
(6 answers)
Closed 10 months ago.
I'm trying to compile assimp using MinGW.
I run the commands
cmake CMakeLists.txt -G "MinGW Makefiles" -Wno-error
cmake --build .
but when the project builds I still get an error and the build fails.
The error:
In file included from C:\godijustwantittowork\include\assimp-5.2.3\contrib\unzip\ioapi.c:22:
C:\godijustwantittowork\include\assimp-5.2.3\contrib\unzip\ioapi.c: In function 'ftell64_file_func':
C:\godijustwantittowork\include\assimp-5.2.3\contrib\unzip\ioapi.h:39:21: error: implicit declaration of function 'ftello'; did you mean 'ftell'? [-Werror=implicit-function-declaration]
39 | # define ftello64 ftello
| ^~~~~~
C:\godijustwantittowork\include\assimp-5.2.3\contrib\unzip\ioapi.c:245:11: note: in expansion of macro 'ftello64'
245 | ret = ftello64(ioposix->file);
| ^~~~~~~~
C:\godijustwantittowork\include\assimp-5.2.3\contrib\unzip\ioapi.c: In function 'fseek64_file_func':
C:\godijustwantittowork\include\assimp-5.2.3\contrib\unzip\ioapi.h:40:21: error: implicit declaration of function 'fseeko'; did you mean 'fseek'? [-Werror=implicit-function-declaration]
40 | # define fseeko64 fseeko
| ^~~~~~
C:\godijustwantittowork\include\assimp-5.2.3\contrib\unzip\ioapi.c:303:9: note: in expansion of macro 'fseeko64'
303 | if (fseeko64(ioposix->file, offset, fseek_origin) != 0)
| ^~~~~~~~
cc1.exe: all warnings being treated as errors
code\CMakeFiles\assimp.dir\build.make:3049: recipe for target 'code/CMakeFiles/assimp.dir/__/contrib/unzip/ioapi.c.obj' failed
mingw32-make.exe[2]: *** [code/CMakeFiles/assimp.dir/__/contrib/unzip/ioapi.c.obj] Error 1
CMakeFiles\Makefile2:249: recipe for target 'code/CMakeFiles/assimp.dir/all' failed
mingw32-make.exe[1]: *** [code/CMakeFiles/assimp.dir/all] Error 2
Makefile:147: recipe for target 'all' failed
mingw32-make.exe: *** [all] Error 2
Couldn't find an answer on here so sorry if this is a duplicate.

Answer 1

Passing -Wno-error to cmake doesn't magically cause CMake to pass that flag to any and all compilers for any and all languages.
To pass a flag to the C compiler, put CFLAGS=-Wno-error on your CMake command line. See e.g. this answer. You may need to clear your CMake cache.
Also note that this is unlikely to help you, because suppressing the implicit declaration warning still doesn't make those ftello and fseeko functions available.