On Windows, or at least when cross-built with Mingw-w64, build fails
because strict prototype fails on an included file (thus nothing we can
do about in json-c code):
> from /home/jehan/dev/src/json-c/json_util.c:44:
> /home/jehan/.local/share/crossroad/roads/w64/json-c/include/minwindef.h:196:3: error: function declaration isn't a prototype [-Werror=strict-prototypes]
> 196 | typedef INT_PTR (WINAPI *FARPROC) ();
> | ^~~~~~~
> /home/jehan/.local/share/crossroad/roads/w64/json-c/include/minwindef.h:197:3: error: function declaration isn't a prototype [-Werror=strict-prototypes]
> 197 | typedef INT_PTR (WINAPI *NEARPROC) ();
> | ^~~~~~~
> /home/jehan/.local/share/crossroad/roads/w64/json-c/include/minwindef.h:198:3: error: function declaration isn't a prototype [-Werror=strict-prototypes]
> 198 | typedef INT_PTR (WINAPI *PROC) ();
> | ^~~~~~~
Let's just disable the errors for Windows build.
This is a recent regression since commit
6359b79847 which added various assert(0)
calls (often replacing return-s).
With Ming-W64 compiler, json-c build was failing with various errors of
the sort:
> /home/jehan/dev/src/json-c/json_object.c: In function 'json_object_int_inc':
> /home/jehan/dev/src/json-c/json_object.c:841:1: error: control reaches end of non-void function [-Werror=return-type]
> 841 | }
> | ^
> In file included from /home/jehan/dev/src/json-c/json_object.c:17:
> /home/jehan/dev/src/json-c/json_object.c: In function 'json_object_get_double':
> /home/jehan/.local/share/crossroad/roads/w64/json-c/include/assert.h:76:4: error: this statement may fall through [-Werror=implicit-fallthrough=]
> 76 | (_assert(#_Expression,__FILE__,__LINE__),0))
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> /home/jehan/dev/src/json-c/json_object.c:1070:7: note: in expansion of macro 'assert'
> 1070 | assert(0);
> | ^~~~~~
> /home/jehan/dev/src/json-c/json_object.c:1072:3: note: here
> 1072 | case json_type_boolean:
> | ^~~~
The problem is that Mingw-w64 does not consider assert() as a noreturn
(even assert(0)), because it has to be compatible by Microsoft
libraries. See the discussion here:
https://sourceforge.net/p/mingw-w64/bugs/306/
Instead let's create a new json_abort() function which is basically just
an abort() function with an optional message, for such cases where
abortion was non-conditional (using assert() and using the assertion
condition as a message here was clearly a misuse of the function). And
mark json_abort() as 'noreturn', as well as 'cold' for optimization
purpose (this is code we expect to never run, unless there is a bug,
that is).
Finally let's use this json_abort() instead of previous misused assert()
calls.
CMake was not properly substituting the installation dir variables (they
ended up all empty), so the pkg-config results were also wrongs. For
instance cflags was: -I -I/json-c
Even though json-c was found at configure time, this obviously broke the
build of any application using it.
AC_FUNC_REALLOC is messed up when cross-compiling, ending up in failed
build with "undefined reference to `rpl_realloc'" error.
AC_CHECK_FUNCS will work both with native and cross builds.
Jehan