illumos gate

Currently, if one has code that crashes in one of the libc string functions (e.g. strlen), the resulting stack trace from pstack(1) or in mdb(1) always misses a frame. That is, for the following (contrived) code:

static void
foo(void)
{
    strlen(NULL);
}

static void
bar(void)
{
    foo();
}

int
main(void)
{
    bar();
    return 0;
}

The resulting core file will show main and foo, but not bar in the stack trace. This is because the string functions in libc are written in assembly, but do not manipulate the frame pointer %ebp/%rbp on function entry/exit (unlike the C functions). The fix is to utilize the frame pointer (push %[er]bp; mov %[er]sp, %[er]bp at the start of a function, and pop %ebp/leave at the end of a function) as the compiled C code does.

Note that the kernel uses C versions of these functions, so is not effected by this.