Stack overflow when adding link dependency. Available stack reduced with linking?

Problem

I get a stack overflow if I link against a library, and I don't get it if I don't. Here is the code:

#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

#define ASSERT_FATAL(cond) \
    do { if (!(cond))  { printf("FAILED COND\n"); exit(-1); }  } while(0)

void *func(void *dummy) {
    // let's make sure the compiler doesn't optimize this out
    volatile char buf[80000];
    for (int i = 0; i < sizeof(buf); ++i)
        buf[i] = rand()  % 128;

    sleep(1);
    printf("Thread finished\n");
}

int main() {
    pthread_t thread_id;
    pthread_attr_t attr;

    ASSERT_FATAL(pthread_attr_init(&attr) == 0);
    ASSERT_FATAL(pthread_attr_setstacksize(&attr, 100000) == 0);
    ASSERT_FATAL(pthread_create(&thread_id, &attr, func, NULL) == 0);

    pthread_attr_destroy(&attr);

    sleep(2);
    return 0;
}

To reproduce:

• Runs fine with gcc test.c -pthread -O3
• Crashes with stack overflow with gcc test.c -pthread -O3 -Wl,--no-as-needed /usr/lib/x86_64-linux-gnu/libcholmod.so -Wl,--as-needed

NOTE: I use cholmod because that was the source of my problems in a larger codebase. In Ubuntu you can get it by installing libsuitesparse-dev.

My question

What's going on here? If I increase stack size it will work, but I want to understand what's causing it. Can the .so file do per-thread initialization and somehow reduce available stack space?

EDIT 1: changed all C++ code for pure C code

EDIT 2: assert result of thread creation/attribute setting