Potential Bug Detected in string.c

[xyzxyzaabbcc]

Hello,

We have developed an automatic vulnerability detector, and it has identified a potential defect in your open source project. Here are the details:

File: string.c Line Number: 27 Method/Function: format

Description of the Issue: My tool detected a potential null dereference bug in the above-mentioned location. This could potentially lead to undefined behavior of vfprintf function.

Here is the relevant code snippet:

FILE *out = open_memstream(&buf, &buflen);

va_list ap;
va_start(ap, fmt);
vfprintf(out, fmt, ap);

Suggested Fix: add a if statement to handle the situation that open_memstream fails and return a NULL value.

I hope this helps improve the project!

Best, xyzxyzaabbcc