Build failure with recent version of clang

[Sylvain Defresne]

When trying to build with a recent version of clang (a218706cba90248be0c60bd6a8f10dbcf0270955), it fails with the following error:

clang -MMD -MT build/ninja/linux/release/x86-64/rpmalloc-a8e50b6/rpmalloc-65d008a.o -MF build/ninja/linux/release/x86-64/rpmalloc-a8e50b6/rpmalloc-65d008a.o.d -I.  -DRPMALLOC_COMPILE=1 -funit-at-a-time -fstrict-aliasing -fvisibility=hidden -fno-stack-protector -fomit-frame-pointer -fno-math-errno -ffinite-math-only -funsafe-math-optimizations -fno-trapping-math -ffast-math -D_GNU_SOURCE=1 -W -Werror -pedantic -Wall -Weverything -Wno-c++98-compat -Wno-padded -Wno-documentation-unknown-command -Wno-implicit-fallthrough -Wno-static-in-inline -Wno-reserved-id-macro -Wno-disabled-macro-expansion -std=c11 -m64 -g -DBUILD_RELEASE=1 -O3 -funroll-loops -DENABLE_PRELOAD=1 -DENABLE_OVERRIDE=1 --target=x86_64-linux-gnu --sysroot=/b/s/w/ir/x/w/cipd/sysroot -c rpmalloc/rpmalloc.c -o build/ninja/linux/release/x86-64/rpmalloc-a8e50b6/rpmalloc-65d008a.o
rpmalloc/rpmalloc.c:869:6: error: mixing declarations and code is incompatible with standards before C99 [-Werror,-Wdeclaration-after-statement]
        int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_UNINITIALIZED;
            ^
rpmalloc/rpmalloc.c:1108:11: error: mixing declarations and code is incompatible with standards before C99 [-Werror,-Wdeclaration-after-statement]
                        size_t remain_count = reserved_count - _memory_heap_reserve_count;
                               ^

This is because -Weverything enables all warnings, even those that are incompatible with the selected standard ("because its point is to enable all warnings, no matter if they make sense or not. (Maybe you want to build your code with a newer standard but keep it somewhat compatible with the old standard or something like that)").

Adding -Wno-declaration-after-statement to the clang command-line suppress this warning and allow the build to succeed.

[Mattias Jansson]

Sigh, warning about standards before C99 when -std=c11 is present on command line, wonderful ... I'll just add that to the command line then.

[David Turner]

Unfortunately, the issue still isn't fixed due to the fact that the first commit in the PR added the right Clang compiler flags, but the second one, which address MacOS issues, removed it!

[1] e0e00ff
[2] f2b3c49

Can we re-open this issue, or get a fix instead?

[Mattias Jansson]

Oh crap 😢 I reapplied the commit on develop branch, hope it works now.

[David Turner]

Well, that happens, thanks for the quick fix :) I confirm that this fixes the issue for us!