https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106767
--- Comment #5 from Alexey Izbyshev <izbyshev at ispras dot ru> ---
(In reply to Richard Biener from comment #4)
> Is there a public specification of the Microsoft extension and how it is
> supposed to behave with recursion or is the recursion behavior specified
> by the C standard?
I would be surprised if anything that could be called "a public specification"
exists. The Clang patch[1] from 2010 cites only the rudimentary MSDN
documentation[2].
I've modified the first test case to be compilable to assembler to avoid
relying on broken /E:
#define P(x) _Pragma(#x)
#define f() P(push_macro("f")) P(pop_macro("f")) f()
int f() {
return 42;
}
and have checked that:
* All x64 MSVC versions supporting C99 _Pragma and available at godbolt
(19.25-19.33/latest) successfully compile it (with and without /Zc:preprocessor
option which enables standard-conforming preprocessor, where it's supported).
The only exception is 19.26 with /Zc:preprocessor: it emits strange syntax
errors, but that's likely a bug in the new preprocessor (19.26 is the first
version supporting it).
* All x64 MSVC versions available at godbolt (19.0, 19.10, 19.14-19.33/latest)
successfully compile the same test case with _Pragma(#x) replaced with
MSVC-specific __pragma(x) equivalent (again, with and without /Zc:preprocessor
where supported).
This suggests that push/pop_macro isn't supposed to interfere with recursion
detection.
[1]
https://github.com/llvm/llvm-project/commit/c0a585d63c6cf700ea01f1fe30c9f4cd51c1e97b
[2] https://docs.microsoft.com/en-us/cpp/preprocessor/push-macro
