wgrib 3.5.0 fails to build with gcc 15

[opoplawski]

gcc 15 is now in Fedora rawhide. wgrib2 fails to build with it by default due to the change to the C23 standard. Errors include:

[ 21%] Building C object wgrib2/CMakeFiles/wgrib2_lib.dir/fnlist.c.o
cd /builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/redhat-linux-build/wgrib2 && /usr/bin/gcc -Dwgrib2_lib_EXPORTS -I/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/redhat-linux-build -I/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/gctpc/source/include -g -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -m64 -march=x86-64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -mtls-dialect=gnu2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -DGFORTRAN -fPIC -fopenmp -MD -MT wgrib2/CMakeFiles/wgrib2_lib.dir/fnlist.c.o -MF CMakeFiles/wgrib2_lib.dir/fnlist.c.o.d -o CMakeFiles/wgrib2_lib.dir/fnlist.c.o -c /builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:9:12: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **)’ [-Wincompatible-pointer-types]
    9 |    {"else",f_else, Else, 0, "else, -if ... -else ... -endif", 100},
      |            ^~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:9:12: note: (near initialization for ‘functions[0].fn’)
In file included from /builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:4:
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:11:5: note: ‘f_else’ declared here
   11 | int f_else(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local);
      |     ^~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:10:14: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **, const char *)’ [-Wincompatible-pointer-types]
   10 |    {"elseif",f_if, Elseif, 1, "elseif X (POSIX regular expression) conditional on match, -if ... -elseif ... -endif", 200},
      |              ^~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:10:14: note: (near initialization for ‘functions[1].fn’)
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:18:5: note: ‘f_if’ declared here
   18 | int f_if(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local, const char *arg1);
      |     ^~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:11:17: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **, const char *)’ [-Wincompatible-pointer-types]
   11 |    {"elseif_fs",f_if_fs, Elseif, 1, "elseif X (fixed string) conditional execution", 200},
      |                 ^~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:11:17: note: (near initialization for ‘functions[2].fn’)
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:20:5: note: ‘f_if_fs’ declared here
   20 | int f_if_fs(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local, const char *arg1);
      |     ^~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:12:16: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **, const char *)’ [-Wincompatible-pointer-types]
   12 |    {"elseif_n",f_if_n, Elseif, 1, "elseif (inv numbers in range), X=(start:end:step)", 200},
      |                ^~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:12:16: note: (near initialization for ‘functions[3].fn’)
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:21:5: note: ‘f_if_n’ declared here
   21 | int f_if_n(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local, const char *arg1);
      |     ^~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:13:18: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **, const char *)’ [-Wincompatible-pointer-types]
   13 |    {"elseif_rec",f_if_rec, Elseif, 1, "elseif (record numbers in range), X=(start:end:step)", 200},
      |                  ^~~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:13:18: note: (near initialization for ‘functions[4].fn’)
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:22:5: note: ‘f_if_rec’ declared here
   22 | int f_if_rec(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local, const char *arg1);
      |     ^~~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:14:18: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **, const char *)’ [-Wincompatible-pointer-types]
   14 |    {"elseif_reg",f_if_reg, Elseif, 1, "elseif rpn registers defined, X = A, A:B, A:B:C, etc A = register number", 200},
      |                  ^~~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:14:18: note: (near initialization for ‘functions[5].fn’)
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:23:5: note: ‘f_if_reg’ declared here
   23 | int f_if_reg(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local, const char *arg1);
      |     ^~~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:15:13: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **)’ [-Wincompatible-pointer-types]
   15 |    {"endif",f_endif, Endif, 0, "terminates if block", 100},
      |             ^~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:15:13: note: (near initialization for ‘functions[6].fn’)
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:17:5: note: ‘f_endif’ declared here
   17 | int f_endif(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local);
      |     ^~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:16:10: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **, const char *)’ [-Wincompatible-pointer-types]
   16 |    {"if",f_if, If, 1, "if X (POSIX regular expression), conditional execution on match", 100},
      |          ^~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:16:10: note: (near initialization for ‘functions[7].fn’)
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:18:5: note: ‘f_if’ declared here
   18 | int f_if(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local, const char *arg1);
      |     ^~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:17:24: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **)’ [-Wincompatible-pointer-types]
   17 |    {"if_delayed_error",f_if_delayed_error, If, 0, "if delayed error", 100},
      |                        ^~~~~~~~~~~~~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:17:24: note: (near initialization for ‘functions[8].fn’)
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.h:19:5: note: ‘f_if_delayed_error’ declared here
   19 | int f_if_delayed_error(int mode, unsigned char **sec, float *data, unsigned int ndata, char *inv, void **local);
      |     ^~~~~~~~~~~~~~~~~~
/builddir/build/BUILD/wgrib2-3.5.0-build/wgrib2-3.5.0/wgrib2/fnlist.c:18:13: error: initialization of ‘int (*)(void)’ from incompatible pointer type ‘int (*)(int,  unsigned char **, float *, unsigned int,  char *, void **, const char *)’ [-Wincompatible-pointer-types]
   18 |    {"if_fs",f_if_fs, If, 1, "if X (fixed string), conditional execution on match", 100},
      |             ^~~~~~~

this is just a few but I think you get the gist. See https://gcc.gnu.org/gcc-15/porting_to.html#c23 for some more info.