libfastjson: indicate explicitly which gcc -std option to use

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"Thomas" == Thomas Petazzoni <[email protected]> writes:

This commit fixes the following build issue of libfastjson with old enough compilers (4.8) and wchar disabled:

json_object.c: In function 'fjson_object_object_delete':
json_object.c:385:3: error: 'for' loop initial declarations are only allowed in C99 mode

   for (int i = 0 ; i < FJSON_OBJECT_CHLD_PG_SIZE ; ++i) {
   ^

The code of libfastjson requires C99. If your compiler is recent enough (gcc 5.x), then no problem, it is C99 by default, no additional flags are needed.

If your compiler is older (for example gcc 4.8), then -std=c99 or -std=gnu99 is explicitly needed to tell the compiler to accept C99 constructs. Testing the compiler for the availability of such flags is done by libfastjson configure script. However, the test program used by the configure script uses some wchar_t types, and therefore the test checking for C99 availability fails on toolchains with wchar disabled. From config.log:

configure:3928: checking for /home/test/buildroot/output/host/usr/bin/i586-buildroot-linux-uclibc-gcc option to accept ISO C99
[...]
configure:4077: /home/test/buildroot/output/host/usr/bin/i586-buildroot-linux-uclibc-gcc -std=gnu99 -c -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 conftest.c >&5 conftest.c:54:3: error: unknown type name 'wchar_t'

   const wchar_t *name;
   ^

So, just like we did in libv4l in commit f01396a158f14c53b781c35f7ff29da0bea8c8d6 ("libv4l: fix uclibc-ng configure/compile"), let's hint directly the configure script that it should use -std=gnu99. This fixes the build of libfastjson with old compilers and wchar disabled.

Signed-off-by Thomas Petazzoni <[email protected]>

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"Thomas" == Thomas Petazzoni <[email protected]> writes:

This commit fixes the following build issue of libfastjson with old enough compilers (4.8) and wchar disabled:

json_object.c: In function 'fjson_object_object_delete':
json_object.c:385:3: error: 'for' loop initial declarations are only allowed in C99 mode

   for (int i = 0 ; i < FJSON_OBJECT_CHLD_PG_SIZE ; ++i) {
   ^

The code of libfastjson requires C99. If your compiler is recent enough (gcc 5.x), then no problem, it is C99 by default, no additional flags are needed.

If your compiler is older (for example gcc 4.8), then -std=c99 or -std=gnu99 is explicitly needed to tell the compiler to accept C99 constructs. Testing the compiler for the availability of such flags is done by libfastjson configure script. However, the test program used by the configure script uses some wchar_t types, and therefore the test checking for C99 availability fails on toolchains with wchar disabled. From config.log:

configure:3928: checking for /home/test/buildroot/output/host/usr/bin/i586-buildroot-linux-uclibc-gcc option to accept ISO C99
[...]
configure:4077: /home/test/buildroot/output/host/usr/bin/i586-buildroot-linux-uclibc-gcc -std=gnu99 -c -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 conftest.c >&5 conftest.c:54:3: error: unknown type name 'wchar_t'

   const wchar_t *name;
   ^

So, just like we did in libv4l in commit f01396a158f14c53b781c35f7ff29da0bea8c8d6 ("libv4l: fix uclibc-ng configure/compile"), let's hint directly the configure script that it should use -std=gnu99. This fixes the build of libfastjson with old compilers and wchar disabled.

Signed-off-by Thomas Petazzoni <[email protected]>