https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99066
Bug ID: 99066
Summary: non-weak definition emitted for explicit instantiation
declaration
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Keywords: link-failure
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
If two TUs both include a header that contains:
template <typename a> struct basic_string {
static const int npos = 1;
};
template <typename a> const int basic_string<a>::npos;
struct e { template <bool> int f() const; };
template <bool> int e::f() const {
return basic_string<char>::npos;
}
extern template class basic_string<char>;
then we get a linker error, because both TUs define the npos constant:
/usr/bin/ld: /tmp/ccjy3Spq.o:(.rodata+0x0): multiple definition of
`basic_string<char>::npos'; /tmp/ccMQ33nr.o:(.rodata+0x0): first defined here
Shouldn't the static data member only have weak definitions, unless an explicit
instantiation definition is seen?
/* TU 1 */
#include "str.h"
int main()
{
return e().f<true>();
}
/* TU 2 */
#include "str.h"
The assembly for both files contains:
.globl _ZN12basic_stringIcE4nposE
.section .rodata
.align 4
.type _ZN12basic_stringIcE4nposE, @object
.size _ZN12basic_stringIcE4nposE, 4
_ZN12basic_stringIcE4nposE:
.long 1
