https://sourceware.org/bugzilla/show_bug.cgi?id=26678
Bug ID: 26678
Summary: construction vtable defined in a discarded section
Product: binutils
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: gold
Assignee: ccoutant at gmail dot com
Reporter: cassio.neri at gmail dot com
CC: ian at airs dot com
Target Milestone: ---
This might be a compiler bug but I get the felling it's the linker. To
reproduce you need g++ and clang++ and a quite strange example spread across 3
files:
// a.hpp
struct A {
int i;
~A() { asm("" : "=r"(i)); }
};
struct B : public virtual A { };
struct C : public B { };
struct D {
D(C);
};
// a.cpp
#include "a.hpp"
void f(C) {
}
D::D(C c) {
f(c);
}
// main.cpp
#include "a.hpp"
int main() {
C c;
D d(c);
}
Build with:
g++ -O3 -fPIC -c a.cpp
clang++ -O3 -fPIC -c main.cpp
clang++ -fuse-ld=gold main.o a.o -o main
The output is:
a.o:a.cpp:function D::D(C) [clone .cold]: error: relocation refers to global
symbol "construction vtable for B-in-C", which is defined in a discarded
section
section group signature: "_ZTV1C"
prevailing definition is from main.o
clang-10: error: linker command failed with exit code 1 (use -v to see
invocation)
FWIW: All the ingredients in the example seem relevant (asm, virtual
inheritance, levels of indirection, compiler flags) and the issue goes away if
any is removed. More notable changes that make the issue go away are:
1. Use the same compiler for all TUs, (It doesn't matter whether g++ or
clang++.)
2. Link with ld (i.e., remove -fuse-ld=gold)
3. Compile main.cpp without -O3.
4. Compile main.cpp without -fPIC.
5. Swap a.o and main.o in the linker command line.
For more information: https://stackoverflow.com/q/64118757/1137388
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