Re: [FFmpeg-devel] [PATCH 1/5] configure: remove build-time check for gzip support in zlib

[Timo Rothenpieler <timo@rothenpieler.org>]

On 27.05.2025 03:33, Ramiro Polla wrote:
> We currently test at build-time whether zlib supports decoding gzip.
> This is not needed for the build to succeed, since only the gzip
> command is necessary to perform compression at build-time.
> 
> Presumably this check will help the user by not enabling compression at
> build-time if their system won't be able to decompress at runtime.
> 
> But there are no guarantees that the system where the build is made is
> the same system where it will run. The build system could support gzip
> in zlib, but not the system at runtime, or the other way around.
> 
> Realistically, the chances of there being a system where zlib does not
> support gzip are very slim. It is safe to assume that zlib will support
> gzip.
> 
> This commit changes the dependency for support of compressed resources
> and ptx files to normal zlib support, and the existence of the gzip
> command.
> ---
>   configure | 13 ++-----------
>   1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/configure b/configure
> index 3730b0524c..79c4fcf327 100755
> --- a/configure
> +++ b/configure
> @@ -2548,7 +2548,6 @@ HAVE_LIST="
>       posix_ioctl
>       texi2html
>       xmllint
> -    zlib_gzip
>       openvino2
>   "
>   
> @@ -6895,19 +6894,11 @@ enabled  zlib && { check_pkg_config zlib zlib "zlib.h" zlibVersion ||
>   enabled bzlib && check_lib bzlib bzlib.h BZ2_bzlibVersion    -lbz2
>   enabled  lzma && check_lib lzma   lzma.h lzma_version_number -llzma
>   
> -enabled zlib && test_exec $zlib_extralibs <<EOF && enable zlib_gzip
> -#include <zlib.h>
> -int main(void) {
> -    if (zlibCompileFlags() & (1 << 17)) return 1;
> -    return 0;
> -}
> -EOF
> -
>   [ -x "$(command -v gzip)" ] && enable gzip
>   
> -enabled zlib_gzip && enabled gzip || disable ptx_compression
> +enabled zlib && enabled gzip || disable ptx_compression
>   
> -enabled zlib_gzip && enabled gzip || disable resource_compression
> +enabled zlib && enabled gzip || disable resource_compression
>   
>   # On some systems dynamic loading requires no extra linker flags
>   check_lib libdl dlfcn.h "dlopen dlsym" || check_lib libdl dlfcn.h "dlopen dlsym" -ldl

I don't see why this should be removed.
It does not hurt in any way, and can prevent bad surprises for people 
building in odd environments where zlib for some reason does not support 
this.

Chances are high that if the build env doesn't support it, neither will 
the intended runtime env.
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