[clang] [WIP][clang] Fix std::tm etc. mangling on Solaris (PR #106353)

[Rainer Orth via cfe-commits]

https://github.com/rorth created https://github.com/llvm/llvm-project/pull/106353

Recently, Solaris bootstrap got broken because Solaris uses a non-standard mangling of `std::tm` and a few others.  This was fixed with a hack in PR Solaris ABI requirements, mangling `std::tm` as `tm` and similarly for `std::div_t`, `std::ldiv_t`, and `std::lconv`.

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

Unfortunately, this patch is almost there, but not quite yet: while the new testcase works as expected, the original trigger in `clang/lib/Lex/PPMacroExpansion.cpp` is now mangled into `_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_RSt8ios_basecPK2tmPKcSA_` (`std::time_put<char, std::ostreambuf_iterator<char, std::char_traits<char>> >::put(std::ostreambuf_iterator<char,std::char_traits<char> >,std::ios_base&, char, tm const*, char const*, char const) const`) instead of the expected
`_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_RSt8ios_basecPK2tmPKcSB_` (`std::time_put<char, std::ostreambuf_iterator<char, std::char_traits<char>> >::put(std::ostreambuf_iterator<char,std::char_traits<char> >,std::ios_base&, char, tm const*, char const*, char const*) const`), i.e. `char const` for the final arg instead of `char const*`.  I don't have the slightest idea why, unfortunately.

>From 646c6ad032fe9c15faee03246496958f7592ea75 Mon Sep 17 00:00:00 2001
From: Rainer Orth <ro at gcc.gnu.org>
Date: Wed, 28 Aug 2024 11:24:29 +0200
Subject: [PATCH] [WIP][clang] Fix std::tm etc. mangling on Solaris

Recently, Solaris bootstrap got broken because Solaris uses a non-standard
mangling of `std::tm` and a few others.  This was fixed with a hack in PR
Solaris ABI requirements, mangling `std::tm` as `tm` and similarly for
`std::div_t`, `std::ldiv_t`, and `std::lconv`.

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

Unfortunately, this patch is almost there, but not quite yet: while the new
testcase works as expected, the original trigger in
`clang/lib/Lex/PPMacroExpansion.cpp` is now mangled into
`_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_RSt8ios_basecPK2tmPKcSA_`
(`std::time_put<char, std::ostreambuf_iterator<char, std::char_traits<char>
> >::put(std::ostreambuf_iterator<char, std::char_traits<char> >,
std::ios_base&, char, tm const*, char const*, char const) const`) instead
of the expected
`_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_RSt8ios_basecPK2tmPKcSB_`
(`std::time_put<char, std::ostreambuf_iterator<char, std::char_traits<char>
> >::put(std::ostreambuf_iterator<char, std::char_traits<char> >,
std::ios_base&, char, tm const*, char const*, char const*) const`),
i.e. `char const` for the final arg instead of `char const*`.  I don't have
the slightest idea why, unfortunately.
---
 clang/lib/AST/ItaniumMangle.cpp    | 22 ++++++++++++++++++++++
 clang/lib/Lex/PPMacroExpansion.cpp |  6 ++++--
 clang/test/AST/solaris-tm.cpp      | 27 +++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/AST/solaris-tm.cpp

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 976670d1efa561..12c926d589b3dc 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -38,6 +38,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TargetParser/RISCVTargetParser.h"
 #include <optional>
+#include <set>
 
 using namespace clang;
 
@@ -6953,6 +6954,27 @@ bool CXXNameMangler::mangleStandardSubstitution(const NamedDecl *ND) {
     return false;
   }
 
+  if (getASTContext().getTargetInfo().getTriple().isOSSolaris()) {
+    if (const RecordDecl *RD = dyn_cast<RecordDecl>(ND)) {
+      if (!isStdNamespace(Context.getEffectiveDeclContext(RD)))
+        return false;
+
+      // Issue #33114: Need non-standard mangling of std::tm etc. for
+      // Solaris ABI compatibility.
+      static std::set<StringRef> types{"div_t", "ldiv_t", "lconv", "tm"};
+
+      // <substitution> ::= tm # ::std::tm, same for the others
+      if (const IdentifierInfo *II = RD->getIdentifier()) {
+        StringRef type = II->getName();
+        if (types.count(type)) {
+          Out << type.size() << type;
+          return true;
+        }
+      }
+      return false;
+    }
+  }
+
   return false;
 }
 
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 1d671ab72b0c03..a8991c28f0261f 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1604,10 +1604,12 @@ static bool isTargetVariantEnvironment(const TargetInfo &TI,
   return false;
 }
 
-#if defined(__sun__) && defined(__svr4__)
+#if defined(__sun__) && defined(__svr4__) && defined(__clang__) &&             \
+    __clang__ < 20
 // 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).
+// (PR #99075).  clang 20 contains a fix, but the workaround is still needed
+// with older versions.
 asm("_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_"
     "RSt8ios_basecPKSt2tmPKcSB_ = "
     "_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_"
diff --git a/clang/test/AST/solaris-tm.cpp b/clang/test/AST/solaris-tm.cpp
new file mode 100644
index 00000000000000..f3d16b7ba1116f
--- /dev/null
+++ b/clang/test/AST/solaris-tm.cpp
@@ -0,0 +1,27 @@
+/// Check that std::tm and a few others are mangled as tm on Solaris only.
+/// Issue #33114.
+///
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple amd64-pc-solaris2.11 | FileCheck --check-prefix=CHECK-SOLARIS %s
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple x86_64-unknown-linux-gnu  | FileCheck --check-prefix=CHECK-LINUX %s
+//
+// REQUIRES: x86-registered-target
+//
+// CHECK-SOLARIS: @_Z6tmfunc2tm
+// CHECK-SOLARIS: @_Z7ldtfunc6ldiv_t
+// CHECK-LINUX:   @_Z6tmfuncSt2tm
+// CHECK-LINUX:   @_Z7ldtfuncSt6ldiv_t
+
+namespace std {
+  extern "C" {
+    struct tm {
+      int tm_sec;
+    };
+    struct ldiv_t {
+      long quot;
+    };
+  }
+}
+
+void tmfunc (std::tm tm) {}
+
+void ldtfunc (std::ldiv_t ldt) {}