[x86_64] gdb: Cannot find thread-local variables on this target
Initially discovered while working on the D packages, as D uses TLS by default for global variables, but this reproduces easily with C as well.
Code used for example:
#include <stdio.h>
__thread char* value;
void foo (void)
{
value = "Hello World";
}
int main(int argc, char** argv)
{
foo();
printf("%s\n", value);
}
$ apk list gcc gdb
gcc-9.2.0-r5 x86_64 {gcc} (GPL-2.0-or-later LGPL-2.1-or-later) [installed]
gdb-8.3.1-r4 x86_64 {gdb} (GPL-3.0-or-later LGPL-3.0-or-later) [installed]
$ gcc -g foo.c
$ gdb ./a.out
GNU gdb (GDB) 8.3.1
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-alpine-linux-musl".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./a.out...
(gdb) b foo
Breakpoint 1 at 0x119d: file foo.c, line 7.
(gdb) run
Starting program: /home/effortman/aports/testing/dmd/a.out
warning: Error disabling address space randomization: Operation not permitted
Breakpoint 1, foo () at foo.c:7
7 value = "Hello World";
(gdb) p value
Cannot find thread-local storage for process 1551, executable file /home/effortman/aports/testing/dmd/a.out:
Cannot find thread-local variables on this target
(gdb)
Tested on x86_64, haven't checked other architectures, but I doubt it'd work either.
Edited by Mathias LANG