Demo for Zig's stack trace behaviour in C

include.h

void foo(int n);

main.c

#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>

void assert(bool ok);
size_t my_strlen(const char s[static 1]);
void bar(void);

void foo(int n) {
  assert(n != 0);
  puts("foo");
}

void baz(void) {}

int main(void) {
  assert(my_strlen("foo") == sizeof("foo") - 1);
  bar();
}

Makefile

.PHONY: all clean fclean re

CC = zig cc
# `zig cc` passes `-fsanitize=undefined` by default.
CFLAGS = -Wall -Wextra -Werror -Wconversion #-fsanitize=undefined

SRC = main.c
OBJ = $(SRC:.c=.o) zig.o

demo : $(OBJ)
	$(CC) $(CFLAGS) $(OBJ) -o $@

# `-lc` links to the system's libc found by `zig libc`. Also look at `zig env`.
# `-I<dir>` can be used to include files
# `-fcompiler-rt` is apprently needed in some cases (https://github.com/ziglang/zig/issues/7264)
# `-femit-h` would be nice but is broken as of writing (https://github.com/ziglang/zig/issues/23887)
zig.o : zig.zig include.h
	zig build-obj -lc -I. $<

%.o : %.c
	$(CC) -c $(CFLAGS) $< -o $@

all : demo

clean :
	rm -f $(OBJ)

fclean : clean
	rm -f demo

re : clean all

zig.zig

const std = @import("std");

const c = @cImport({
    @cInclude("include.h");
});

export fn assert(ok: bool) void {
    std.debug.assert(ok);
}

extern fn foo(n: c_int) void;

export fn bar() void {
    c.foo(1);
    foo(0);
}

export fn my_strlen(s: [*:0]const u8) usize {
    var i: usize = 0;
    while (s[i] != 0) : (i += 1) {}
    return (i);
}

// With the following line, it becomes possible to run the program with the following command:
// ```
// $ zig run -I. -lc main.c zig.zig
// ```
pub const _start = void;