[LLVMbugs] [Bug 18408] New: clang-3.5 emits function definition with internal linkage incorrectly

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Jan 7 01:47:47 PST 2014


            Bug ID: 18408
           Summary: clang-3.5 emits function definition with internal
                    linkage incorrectly
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: release blocker
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: ken at fsfoundry.org
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

I use Ubuntu 12.04 and installed clang-3.5 using official repository following
the instructions from http://llvm.org/apt/

$ clang++ --version
Ubuntu clang version 3.5-1~exp1 (trunk) (based on LLVM 3.5)
Target: x86_64-pc-linux-gnu
Thread model: posix

Clang emits function definition incorrectly with internal linkage, when one of
the function's parameters is an instance of, or a pointer to, a template class
taking a nested class template as its template template parameter. This is kind
of mouthful, the code below reproduces the issue.

template <template <class> class A>
struct TemplateTakingTemplateTemplateParameter {};

template <typename B>
class GlobalTemplate {};

struct OutterClass {
    template <typename B>
    class InnerTemplate {};

#if(__cplusplus > 199711L)
    // No template alias pre-C++11
    template <typename B>
    using InnerAliasToGlobalTemplate = GlobalTemplate<B>;

typedef TemplateTakingTemplateTemplateParameter<GlobalTemplate> T1;
typedef TemplateTakingTemplateTemplateParameter<OutterClass::InnerTemplate> T2;
#if(__cplusplus > 199711L)

typedef T1* P1;
typedef T2* P2;
#if(__cplusplus > 199711L)
typedef T3* P3;

void linkageTest(T1) {}
void linkageTest(T2) {}
#if(__cplusplus > 199711L)
void linkageTest(T3) {}
void linkageTest(P1) {}
void linkageTest(P2) {}
#if(__cplusplus > 199711L)
void linkageTest(P3) {}

void test()
#if(__cplusplus > 199711L)
#if(__cplusplus > 199711L)

$ # Using clang to generate IR and grep for "internal"
$ clang++ -std=c++1y -S -emit-llvm internal-linkage.cpp -o - | grep define
define void
#0 {
define void
#0 {
define void @_Z4testv() #1 {
define internal void
#0 {
define internal void
#0 {
define internal void
#0 {
define internal void
#0 {

Note 1: linkageTest(T1) and linkageTest(P1) are emitted correctly without
Note 2: Incorrect code are also emitted when the parameter is a (const)
lval-ref or an rval-ref
Note 3: It doesn't matter which -std is used here. I tried c++98, c++0x, c++11
and c++1y

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