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Fix GH-10751 #10785

Merged
merged 2 commits into from
Mar 7, 2023
Merged

Fix GH-10751 #10785

merged 2 commits into from
Mar 7, 2023

Commits on Mar 7, 2023

  1. */*.m4: update main() signatures. 

    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 soon become an error is -Wstrict-prototypes.
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,

  $ export CFLAGS="$CFLAGS -Werror=strict-prototypes"
  $ ./configure
  ...
  checking if iconv supports errno... no
  configure: error: iconv does not support errno

(this is on a system where iconv *does* support errno). If errno
support were optional, that test would have "silently" disabled
it. The underlying issue here, from config.log, is

  conftest.c:211:5: error: function declaration isn't a prototype
  [-Werror=strict-prototypes]
    211 | int main() {

This commit goes through all of our autoconf tests, replacing main()
with main(void). Up to equivalent types and variable renamings, that's
one of the two valid signatures, and satisfies the compiler (gcc-12 in
this case).

Fixes GH-10751
    @orlitzky
    orlitzky committed Mar 7, 2023
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  2. ext/iconv/config.m4: add missing stdio.h include. 

    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
    @orlitzky
    orlitzky committed Mar 7, 2023
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