older gccs don't accept -Wunused-const-variable
In src/common/compress_zstd.c, we use the
DISABLE_GCC_WARNING() macro to disable the
-Wunused-const-variable warning. Some versions of gcc don't recognize that warning option, so they will warn about incorrect pragma usage.
src/common/compress_zstd.c:29:1: warning: unknown option after ‘#pragma GCC diagnostic’ kind [-Wpragmas] DISABLE_GCC_WARNING(unused-const-variable) ^
We should probably define a macro if
-Wunused-const-variable is supported by gcc and update the preprocessor conditional in compress_zstd.c
#ifdef HAVE_ZSTD DISABLE_GCC_WARNING(unused-const-variable)
to use it.
Reported on IRC.
Confirmed on Xenial with gcc 5.4.0-6ubuntu1~16.04.10 and libzstd1-dev 1.3.1+dfsg-1~ubuntu0.16.04.1. Travis is still on Trusty so doesn't have a libzstd-dev.
This might be a regression on platforms with libzstd but an older gcc.