https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103240
Bug ID: 103240
Summary: std::type_info::before gives wrong answer for ARM EABI
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: ABI
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
Target: arm*-*-*gnueabi
This passes on x86_64 but fails on armv7hl:
// f1.C
#include <typeinfo>
namespace
{
struct S { };
}
std::type_info const& t1 = typeid(S);
// f2.C
#include <typeinfo>
#include <cassert>
extern std::type_info const& t1;
namespace
{
struct S { };
}
std::type_info const& t2 = typeid(S);
int main()
{
if (t1 == t2)
{
assert( !t1.before(t2) );
assert( !t2.before(t1) );
}
else
{
assert( t1.before(t2) || t2.before(t1) );
}
}
$ g++ f1.C f2.C
$ ./a.out
a.out: f2.C:22: int main(): Assertion `t1.before(t2) || t2.before(t1)' failed.
qemu: uncaught target signal 6 (Aborted) - core dumped
Aborted (core dumped)
The problem is in libsupc++/tinfo2.cc
bool
type_info::before (const type_info &arg) const _GLIBCXX_NOEXCEPT
{
#if __GXX_MERGED_TYPEINFO_NAMES
return name () < arg.name ();
#else
return (name ()[0] == '*') ? name () < arg.name ()
: __builtin_strcmp (name (), arg.name ()) < 0;
#endif
}
This should have been fixed like operator== was in r179236 so that it checks
__name[0] not name()[0], otherwise the '*' is skipped and so is never found
there. That means we do a strcmp comparison of the mangled names, even when the
'*' says the types must be compared by pointer address. In the testcase the two
structs have the same mangled name, even though they are distinct types (due to
the unnamed namespaces). The string comparison therefore returns 0, and so
neither type is "before" the other, despite being distinct types.
