Performing C SOURCE FILE Test LIBICONV_SECOND_ARGUMENT_IS_CONST failed with the following output:
Change Dir: /var/tmp/portage/app-i18n/fcitx-4.2.9.8/work/fcitx-4.2.9.8_build/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/ninja cmTC_7d70c && [1/2] Building C object CMakeFiles/cmTC_7d70c.dir/src.c.o
FAILED: CMakeFiles/cmTC_7d70c.dir/src.c.o 
/usr/bin/x86_64-pc-linux-gnu-gcc -DLIBICONV_SECOND_ARGUMENT_IS_CONST   -O2 -pipe -march=x86-64 -frecord-gcc-switches -fno-diagnostics-color -Werror -o CMakeFiles/cmTC_7d70c.dir/src.c.o -c /var/tmp/portage/app-i18n/fcitx-4.2.9.8/work/fcitx-4.2.9.8_build/CMakeFiles/CMakeTmp/src.c
/var/tmp/portage/app-i18n/fcitx-4.2.9.8/work/fcitx-4.2.9.8_build/CMakeFiles/CMakeTmp/src.c: In function ‘main’:
/var/tmp/portage/app-i18n/fcitx-4.2.9.8/work/fcitx-4.2.9.8_build/CMakeFiles/CMakeTmp/src.c:9:21: error: passing argument 2 of ‘iconv’ from incompatible pointer type [-Werror=incompatible-pointer-types]
    9 |         iconv(conv, &in, &ilen, &out, &olen);
      |                     ^~~
      |                     |
      |                     const char **
In file included from /var/tmp/portage/app-i18n/fcitx-4.2.9.8/work/fcitx-4.2.9.8_build/CMakeFiles/CMakeTmp/src.c:2:
/usr/include/iconv.h:42:54: note: expected ‘char ** restrict’ but argument is of type ‘const char **’
   42 | extern size_t iconv (iconv_t __cd, char **__restrict __inbuf,
      |                                    ~~~~~~~~~~~~~~~~~~^~~~~~~
cc1: all warnings being treated as errors
ninja: build stopped: subcommand failed.


Source file was:

    #include <iconv.h>
    int main(){
        iconv_t conv = 0;
        const char* in = 0;
        size_t ilen = 0;
        char* out = 0;
        size_t olen = 0;
        iconv(conv, &in, &ilen, &out, &olen);
        return 0;
    }