Compile warnings in minizip

[jeroen]

We see these warnings when compiling with -Wstrict-prototypes

minizip/ioapi.c:234:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
minizip/zip.c:189:60: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]

[jmcnamara]

Thanks for the report. What OS and compiler version are you using?

[jmcnamara]

I can't reproduce this on macOS:

/tmp$ git clone git@github.com:jmcnamara/libxlsxwriter.git
Cloning into 'libxlsxwriter'...

/tmp$ cd libxlsxwriter/

/tmp/libxlsxwriter$ CFLAGS=-Wstrict-prototypes make V=1 third_party
/Applications/Xcode.app/Contents/Developer/usr/bin/make -C third_party/minizip
cc         -c -Wstrict-prototypes -O3 -DNOCRYPT -DNOUNCRYPT  ioapi.c
cc         -c -Wstrict-prototypes -O3 -DNOCRYPT -DNOUNCRYPT  zip.c
cc -fPIC -c -Wstrict-prototypes -O3 -DNOCRYPT -DNOUNCRYPT  ioapi.c -o ioapi.so
cc -fPIC -c -Wstrict-prototypes -O3 -DNOCRYPT -DNOUNCRYPT  zip.c -o zip.so
/Applications/Xcode.app/Contents/Developer/usr/bin/make -C third_party/tmpfileplus
cc         -c -Wstrict-prototypes  tmpfileplus.c
cc -fPIC -c -Wstrict-prototypes  tmpfileplus.c -o tmpfileplus.so
/Applications/Xcode.app/Contents/Developer/usr/bin/make -C third_party/md5
cc         -c -Wstrict-prototypes  md5.c
cc -fPIC -c -Wstrict-prototypes  md5.c -o md5.so

/tmp/libxlsxwriter (main)$ clang --version
Apple clang version 11.0.0 (clang-1100.0.33.17)

I'll try with some Linux variants.

By the way, the minizip code is third party code from the zlib examples. It may not be warning free with recent compilers. It is probably best not to compile it with additional constraints. It is also possible to link against libminizip so that you don't have to compile it: https://libxlsxwriter.github.io/getting_started.html#gsg_minizip

The libxlsxwriter code itself should be warning clean with -Wstrict-prototypes.

[jeroen]

This happens with clang 15 and gcc 12 (tested on both debian and fedora).

[jmcnamara]

I'll look into it, but since it is third party code it may not be fixed externally in which case it won't be fixable.

Could you disable, or not add that check for that part of the compilation? It is a pretty harmless warning and libxlsxwriter should be warning free.

[jeroen]

This is enforced downstream in the CRAN repository in prep for C23, I cannot disable this unfortunately: https://cran.r-project.org/web/checks/check_results_writexl.html

But I can fix it in my copy of the vendored writexl code, the solution is trivial.

[jmcnamara]

The writexl fix for reference: https://github.com/ropensci/writexl/commit/75c70296260b70b2c08aa412117b4f96c495bfbf

[jmcnamara]

Fixed on main. Thanks for the report.