https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87998
Bug ID: 87998
Summary: defining an alias for a TLS variable
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
In the following snippet the declaration of the alias seems unsafe (or at least
hard to reason about) because it's not clear which thread's variable the alias
is bound to and what happens if the alias is used after the thread exits.
Running the case on x86_64-linux shows the alias is distinct from the TLS
variable in the main thread.
GCC should at least issue a warning for the code if not reject it with an
error.
$ cat t.c && gcc -Wall -Wextra t.c && ./a.out
__thread int a = 123;
extern __attribute ((alias ("a"))) int b;
int main (void)
{
a = 456;
__builtin_printf ("a = %i (@%p)\n" "b = %i (@%p)\n", a, &a, b, &b);
}
a = 456 (@0x7fda5bc9d6fc)
b = 123 (@0x600dfc)
