Failed to detect null derreference using global variable in C

[dgutson]

Please include the following information:

• [x] The version of infer from infer --version.
• [x] Your operating system and version, for example "Debian 9", "MacOS High Sierra", whether you are using Docker, etc.
• [x] Which command you ran, for example infer -- make.
• [x] The full output in a paste, for instance a gist.
• [x] If possible, a minimal example to reproduce your problem (for instance, some code where infer reports incorrectly, together with the way you run infer to reproduce the incorrect report).

This is a spin-off of #1685. Infer version: 1.1.0 OS: WSL 2, Ubuntu 22.04.1, downloaded linux binary Command: infer --pulse-only -F -g --biabduction -- clang b1.c b2.c

b1.c:

int* ptr;

int f()
{
    return *ptr;
}

b2.c:

int f(void);
extern int* ptr;

int main(void)
{
    ptr = 0;
    return f();
}

infer fails to detect the null derreference. However, it does detect it if I pass the null as an argument of f() rather than the global var.