my (failed) attempt at creating a small reproducer for macports bug #36654 (https://trac.macports.org/ticket/36654)

bar.c

__thread int t = 0xdeadbeef;

int foo(void)
{
    return t;
}

build_instructions

clang -g -Wall -dynamiclib -o libbar.dylib bar.c
clang -g -Wall -Wl,-no_pie foo.c -L. -lbar
(the above command was expected to segfault the linker)
./a.out

foo.c

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <sys/wait.h>

extern int foo(void);
extern __thread int t;

int main(int argc, char *argv[])
{
    printf("before change %#x\n", foo());
    t = 0xcafebabe;
    printf("after change %#x\n", foo());
    return 0;
}