Functions without prorotypes cause -Wstrict-prototypes warnings #633
Description
As of Clang 14.0.0, compiling zlib with -Wstrict-prototypes is warning free.
The next Clang release 15.0.0 will include https://reviews.llvm.org/D122895 which has improved diagnostics. Notably: the new -Wdeprecated-non-prototype is enabled by default which warns many declarations in zlib:
% make CC=/tmp/RelA/bin/clang -j 30
/tmp/RelA/bin/clang -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN -I. -I../../ -c -o example.o ../../test/example.c
/tmp/RelA/bin/clang -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN -include zconf.h -c -o adler32.o ../../adler32.c
...
../../compress.c:22:13: warning: a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
int ZEXPORT compress2 (dest, destLen, source, sourceLen, level)
^
../../compress.c:68:13: warning: a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
int ZEXPORT compress (dest, destLen, source, sourceLen)
^
../../compress.c:81:15: warning: a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
uLong ZEXPORT compressBound (sourceLen)
^
../../uncompr.c:27:13: warning: a function declaration without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
int ZEXPORT uncompress2 (dest, destLen, source, sourceLen)
[...]
There are also a few -Wstrict-prototypes -Wno-deprecated-non-prototype diagnostics.
Note: -pedantic will imply -Wstrict-prototypes.
As of GCC 11, its -Wstrict-prototypes warns about some declarations (a small subset of Clang's list):
../../crc32.c:117:16: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
117 | local z_word_t byte_swap(word)
| ^~~~~~~~~
gcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN -include zconf.h -DPIC -c -o objs/gzclose.o ../../gzclose.c
../../crc32.c:717:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
717 | local z_crc_t crc_word(data)
| ^~~~~~~~
../../crc32.c:726:16: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
726 | local z_word_t crc_word_big(data)
| ^~~~~~~~~~~~
../../crc32.c:1093:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
1093 | uLong ZEXPORT crc32_combine_gen64(len2)
| ^~~~~~~~~~~~~~~~~~~