[Bug sanitizer/78267] [7 Regression] libsanitizer breaks bootstrap on x86_64-apple-darwin16 at r241977

[ro at CeBiTec dot Uni-Bielefeld.DE]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78267

--- Comment #40 from ro at CeBiTec dot Uni-Bielefeld.DE <ro at CeBiTec dot Uni-Bielefeld.DE> ---
> --- Comment #37 from Jack Howarth <howarth.at.gcc at gmail dot com> ---
> Created attachment 40045
>   --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40045&action=edit
> preprocessed source for sanitizer_mac.cc from stage3
>
> preprocessed source for sanitizer_mac.cc from stage3 generated with...
[...]
> error: ‘_Static_assert’ was not declared in this scope
>        os_trace("Address Sanitizer reported a failure.");
>        ^~~~~~~~~~~~~~

What a mess: I initially misunderstood this error.  The problem is:
10.11 <os/trace.h> unconditionally uses _Static_assert, which is C11
only, while sanitizer_mac.cc is compiled with -std=gnu++11.  clang++
supports it as an extension, while g++ does not.  One could use

#define _Static_assert static_assert

for C++11 and up, and

#define _Static_assert(x)

otherwise.  However ...

> ../../../../gcc-7-20161114/libsanitizer/sanitizer_common/sanitizer_mac.cc:497:9:
> error: ‘_os_trace_with_buffer’ was not declared in this scope
>        os_trace("Address Sanitizer reported a failure.");
>          ^~~~~~~~~~~~~~~~~~~~~

this one is ugly: os_trace expands to _os_trace_<N>, which all call
_os_trace_with_buffer with a NULL payload.  That declaration is
disabled if !__BLOCKS__, thus the `was not declared' error ;-(

On 10.12, os_trace goes to an OS_TRACE_CALL macro which expands to
nothing for anything but clang 7.3 and up...

The more I look into this chaos, the more attractive I find your patch
to disable <os/trace.h> inclusion if !__BLOCKS__.  Seems we cannot do
better than achieve the same with much more effort.

        Rainer