[libcxx-commits] [PATCH] D74163: [demangler] Fix the parsing of long double literals for PowerPC and S390

[Hubert Tong via Phabricator via libcxx-commits]

hubert.reinterpretcast added a comment.

In D74163#1891047 <https://reviews.llvm.org/D74163#1891047>, @uweigand wrote:

> I'm still wondering about Intel.  Can there ever be a literal encoded using 'g' on Intel?  If yes, then treating it as "long double" would still be wrong, because 'g' encodes IEEE128 (__float128), while "long double" is the Intel extended (80-bit) format, right?


A literal such as `1.Q` would appear as `g3fff0000000000000000000000000000`. As would `1.L` with `-mlong-double-128`.

>> `__cxa_demangle()` is a routine in runtime library libc++abi that is only built natively.
> 
> OK, got it.   Even more so, I guess we must also ensure that it is only built using the default compiler setting (e.g. it is built with the default -mlong-double-128 on s390x, not with -mlong-double-64).  But that's probably a reasonable assumption.

The patch already adds a preprocessor check for that on Power. I've added an inline comment to do the same for s390x.



================
Comment at: libcxxabi/src/cxa_demangle.cpp:11
+    (!defined(__LONG_DOUBLE_128__) || defined(__LONG_DOUBLE_IEEE128__))
+#error "Demangler must be built in double-double long double 128 mode on PPC."
+#endif
----------------
A similar error for building with 64-bit long double on s390x would be appropriate.


Repository:
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