Demangle: only demangle mangled symbols

Only attempt to demangle symbols which have the itanium C++ prefix of `_Z`.
This ensures that we do not treat any symbol name as a managled named.  We would
previously treat a C function `f` as a mangled name and decode that to `float`
incorrectly.

While it is easy to add tests for this, Mehdi recommended against introducing
tests for the demangler as libc++abi should cover the testing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286795 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 1 deletions

diff --git a/lib/Demangle/ItaniumDemangle.cpp b/lib/Demangle/ItaniumDemangle.cpp
index 1d3080c7cb8..39598aad649 100644
--- a/lib/Demangle/ItaniumDemangle.cpp
+++ b/lib/Demangle/ItaniumDemangle.cpp
@@ -4252,6 +4252,16 @@ char *llvm::itaniumDemangle(const char *mangled_name, char *buf, size_t *n,
       *status = invalid_args;
     return nullptr;
   }
+
+  size_t len = std::strlen(mangled_name);
+  if (len < 2 || strncmp(mangled_name, "_Z", 2)) {
+    if (len < 4 || strncmp(mangled_name, "___Z", 4)) {
+      if (status)
+        *status = invalid_mangled_name;
+      return nullptr;
+    }
+  }
+
   size_t internal_size = buf != nullptr ? *n : 0;
   Db db;
   db.cv = 0;
@@ -4263,7 +4273,6 @@ char *llvm::itaniumDemangle(const char *mangled_name, char *buf, size_t *n,
   db.fix_forward_references = false;
   db.try_to_parse_template_args = true;
   int internal_status = success;
-  size_t len = std::strlen(mangled_name);
   demangle(mangled_name, mangled_name + len, db, internal_status);
   if (internal_status == success && db.fix_forward_references &&
       !db.template_param.empty() && !db.template_param.front().empty()) {