[llvm-bugs] [Bug 41645] New: [ThinLTO] externally visible linkonce_odr object is incorrectly internalized
via llvm-bugs
llvm-bugs at lists.llvm.org
Mon Apr 29 01:55:47 PDT 2019
https://bugs.llvm.org/show_bug.cgi?id=41645
Bug ID: 41645
Summary: [ThinLTO] externally visible linkonce_odr object is
incorrectly internalized
Product: new-bugs
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedbugs at nondot.org
Reporter: eleviant at accesssoftek.com
CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org
Symbol with linkonce_odr linkage whose prevailing definition is in regular
object file can be incorrectly internalized by ThinLTO.
Steps to reproduce:
1) Create following C++ source files (struct.h, main.cpp, init.cpp)
// File: struct.h
template <class T>
struct Singleton {
static __attribute__((noinline)) T& getInstance() throw() {
static T instance;
return instance;
}
};
struct S : public Singleton<S> {
long a = 0;
};
static inline S* getS() {
S& os = S::getInstance();
return os.a ? &os : nullptr;
}
// File: main.cpp
#include "struct.h"
void init();
int main() {
init();
return getS()->a;
}
// File: init.cpp
#include "struct.h"
void init() {
S::getInstance().a = 1;
}
2) Compile init.cpp to regular object
clang -c init.cpp
3) Compile main.cpp in thin LTO mode
clang -c -flto=thin main.cpp
4) Link program. It is important that init.o goes before main.o in command line
params
clang -flto=thin -fuse-ld=lld init.o main.o
5) Run a.out. Program will crash because getS() returns zero in main function.
This happens because static instance variable is incorrectly internalized by
thin LTO, so finally init and main functions access two different copies of it.
--
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20190429/404848fa/attachment.html>
More information about the llvm-bugs
mailing list