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Michael Orlitzky
88b30e08cc
The next generation of C compilers is going to enforce the C standard more strictly: https://wiki.gentoo.org/wiki/Modern_C_porting One warning that will eventually become an error is -Wimplicit-function-declaration. This is relatively easy to catch in most code (it will fail to compile), but inside of autoconf tests it can go unnoticed because many feature-test compilations fail by design. For example, AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <iconv.h>]], [[iconv_ccs_init(NULL, NULL);]])]... is designed to fail if iconv_ccs_init() is not in iconv.h. On the other hand, AC_RUN_IFELSE([AC_LANG_SOURCE([[ #include <iconv.h> int main() { printf("%d", _libiconv_version); return 0; } should pass if _libiconv_version is defined. If the user has -Werror=implicit-function-declaration in his CFLAGS, however, it will not: $ export CFLAGS="$CFLAGS -Werror=implicit-function-declaration" $ ./configure ... checking if using GNU libiconv... no This is because the stdio.h header that defines printf() is missing: conftest.c:240:3: error: implicit declaration of function 'printf' [-Werror=implicit-function-declaration] 240 | printf("%d", _libiconv_version); | ^~~~~~ conftest.c:239:1: note: include '<stdio.h>' or provide a declaration of 'printf' This commit adds the include, correcting the test with any compiler that balks at implicit function definitions. Closes GH-10751