[libcxxabi] [llvm] [ItaniumDemangle] Unconditionally parse substitution template arguments (PR #131970)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxxabi

Author: Aiden Grossman (boomanaiden154)

<details>
<summary>Changes</summary>

With the current mangled name parser, when we try to parse a type name inside the template argument of an operator, we end up not parsing any template arguments of substitutions, which ends up causing things to fail in certain cases. This is compliant with the Itanium ABI documentation as far as I can tell.

I tried to look through the git history to find out why the limitation on parsing template arguments for substitutions inside of operators existed, but I only ended up at the import commit, so I suspect the original motivation is lost to time.

A regression test from LLVM has been added.

---
Full diff: https://github.com/llvm/llvm-project/pull/131970.diff


3 Files Affected:

- (modified) libcxxabi/src/demangle/ItaniumDemangle.h (+3-3) 
- (modified) libcxxabi/test/test_demangle.pass.cpp (+1) 
- (modified) llvm/include/llvm/Demangle/ItaniumDemangle.h (+3-3) 


``````````diff
diff --git a/libcxxabi/src/demangle/ItaniumDemangle.h b/libcxxabi/src/demangle/ItaniumDemangle.h
index 3df41b5f4d7d0..45ec8d41fee41 100644
--- a/libcxxabi/src/demangle/ItaniumDemangle.h
+++ b/libcxxabi/src/demangle/ItaniumDemangle.h
@@ -4626,10 +4626,10 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
       //   <template-template-param> ::= <template-param>
       //                             ::= <substitution>
       //
-      // If this is followed by some <template-args>, and we're permitted to
-      // parse them, take the second production.
+      // If this is followed by some <template-args>, take the second
+      // production.
 
-      if (look() == 'I' && (!IsSubst || TryToParseTemplateArgs)) {
+      if (look() == 'I') {
         if (!IsSubst)
           Subs.push_back(Result);
         Node *TA = getDerived().parseTemplateArgs();
diff --git a/libcxxabi/test/test_demangle.pass.cpp b/libcxxabi/test/test_demangle.pass.cpp
index e9c74f70a094b..fad6c101f742d 100644
--- a/libcxxabi/test/test_demangle.pass.cpp
+++ b/libcxxabi/test/test_demangle.pass.cpp
@@ -30247,6 +30247,7 @@ const char* cases[][2] = {
     {"_Z1fDSDRm", "f(_Sat unsigned long _Fract)"},
 
     {"_Z11bfloat16addDF16bDF16b", "bfloat16add(std::bfloat16_t, std::bfloat16_t)"},
+    {"_ZNK4llvm11SmallStringILj16EEcvNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEEv", "llvm::SmallString<16u>::operator std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>() const"},
     // clang-format on
 };
 
diff --git a/llvm/include/llvm/Demangle/ItaniumDemangle.h b/llvm/include/llvm/Demangle/ItaniumDemangle.h
index b0363c1a7a786..15400694b3c70 100644
--- a/llvm/include/llvm/Demangle/ItaniumDemangle.h
+++ b/llvm/include/llvm/Demangle/ItaniumDemangle.h
@@ -4626,10 +4626,10 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
       //   <template-template-param> ::= <template-param>
       //                             ::= <substitution>
       //
-      // If this is followed by some <template-args>, and we're permitted to
-      // parse them, take the second production.
+      // If this is followed by some <template-args>, take the second
+      // production.
 
-      if (look() == 'I' && (!IsSubst || TryToParseTemplateArgs)) {
+      if (look() == 'I') {
         if (!IsSubst)
           Subs.push_back(Result);
         Node *TA = getDerived().parseTemplateArgs();

``````````

</details>


https://github.com/llvm/llvm-project/pull/131970