[clang] [clang] Handle tm mangling on Solaris in PPMacroExpansion.cpp (PR #100724)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Rainer Orth (rorth)

<details>
<summary>Changes</summary>

The introduction of `std::put_time` in
fad17b43dbc09ac7e0a95535459845f72c2b739a broke the Solaris build:
```
Undefined			first referenced
 symbol  			    in file
_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_RSt8ios_basecPKSt2tmPKcSB_ lib/libclangLex.a(PPMacroExpansion.cpp.o)
ld: fatal: symbol referencing errors
```
As discussed in PR #<!-- -->99075, the problem is that GCC mangles `std::tm` as `tm` on Solaris for binary compatility, while `clang` doesn't (Issue #<!-- -->33114).

As a stop-gap measure, this patch introduces an `asm` level alias to the same effect.

Tested on `sparcv9-sun-solaris2.11`, `amd64-pc-solaris2.11`, and `x86_64-pc-linux-gnu`.

---
Full diff: https://github.com/llvm/llvm-project/pull/100724.diff


1 Files Affected:

- (modified) clang/lib/Lex/PPMacroExpansion.cpp (+10) 


``````````diff
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 879f01e87806e..1e31fcc3d731e 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1604,6 +1604,16 @@ static bool isTargetVariantEnvironment(const TargetInfo &TI,
   return false;
 }
 
+#if defined(__sun__) && defined(__svr4__)
+// GCC mangles std::tm as tm for binary compatibility on Solaris (Issue
+// #33114).  We need to match this to allow the std::put_time calls to link
+// (PR #99075).
+asm("_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_"
+    "RSt8ios_basecPKSt2tmPKcSB_ = "
+    "_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_"
+    "RSt8ios_basecPK2tmPKcSB_");
+#endif
+
 /// ExpandBuiltinMacro - If an identifier token is read that is to be expanded
 /// as a builtin macro, handle it and return the next token as 'Tok'.
 void Preprocessor::ExpandBuiltinMacro(Token &Tok) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/100724