llvm-g++ does not mangle method names that match stdlib function names

[llvmbot]

Bugzilla Link	276
Resolution	FIXED
Resolved on	Feb 22, 2010 12:45
Version	trunk
OS	All
Attachments	C++ code demonstrating the problem, Incorrect LLVM assembly output from llvm-g++
Reporter	LLVM Bugzilla Contributor

Extended Description

llvm-g++ does not properly mangle methods that have a name matching one of the C
library functions that might get turned into an LLVM intrinsic.

The attached C code and output LLVM code shows that typical methods get mangled.
However, methods named "strlen" or "memset" do not get mangled properly.

This causes problems with LLVM linking C++ programs, as these methods will get
their types (incorrectly) merged with the function types from the standard C
library.

[llvmbot]

assigned to @lattner

[llvmbot]

Note that the preprocssed code is derived from hbd (the Homebrew Decompiler).

[lattner]

Whoa. That's crazy. I wonder if this is a G++ parser bug or an LLVM bug.

I'll look into it.

-Chris

[lattner]

It looks like this bug is due to the following patch:

$ cvs diff -u -r 1.13 -r 1.14 llvm-expand.c
Index: llvm-expand.c

RCS file:
/home/vadve/vadve/Research/DynOpt/CVSRepository/gcc-3.4/gcc/llvm-expand.c,v
retrieving revision 1.13
retrieving revision 1.14
diff -u -r1.13 -r1.14
--- llvm-expand.c 20 Feb 2004 17:17:28 -0000 1.13
+++ llvm-expand.c 20 Feb 2004 19:08:37 -0000 1.14
@@ -6399,8 +6399,14 @@
PFnTy = llvm_type_get_pointer(FnTy);

if (!DECL_LLVM_SET_P(subr) || DECL_LLVM(subr)->Ty != PFnTy) {

• const char *ExternalName = IDENTIFIER_POINTER(DECL_NAME(subr));

• const char *ExternalName = IDENTIFIER_POINTER(DECL_ASSEMBLER_NAME(subr));
  llvm_value *GlobalVal = llvm_get_global_alias(ExternalName);
• if (!GlobalVal) {

•  ExternalName = IDENTIFIER_POINTER(DECL_NAME(subr));
  

•  GlobalVal = llvm_get_global_alias(ExternalName);
  

•  if (!GlobalVal)
  

•    ExternalName = IDENTIFIER_POINTER(DECL_ASSEMBLER_NAME(subr));
  

• }
  if (!GlobalVal || GlobalVal->Ty != PFnTy) {
  const char *PName = (*lang_hooks.decl_printable_name)(subr, 2);

-Chris

[lattner]

Fixed. Patch here:
http://mail.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20040308/012931.html

Testcase here:
test/Regression/C++Frontend/2004-03-09-UnmangledBuiltinMethods.cpp.tr

-Chris

[llvmbot]

mentioned in issue llvm/llvm-bugzilla-archive#33311