Question

I’m Trying to do:

printf("Provider: %s\n", Props->providerName);

where struct member (from external library) is:

char providerName[256];

causes core dump with gdb output of:

Program terminated with signal 11, Segmentation fault.
[New process 73950    ]
#0  0xfee22290 in strlen () from /lib/libc.so.1

I guess the char[] might not be null terminated, but what is the best solution?

Cheers!

---

edit: The structure I’m using is from an external library, and appears not to be null (I can successfully print another of its members char alias[256];

Answer 1

Use a maximum-width indicator whenever you can when using %s with printf:

printf("Provider: %.255s\n", Props->providerName);

If you still get a segfault, and Props is not NULL, you probably have a clash between your headers and the library binaries. Suppose you have the new version of headers that define:

struct Thing {
    int foo[256];
    int bar[256];
    int baz[256];
};

but the library binaries are outdated, using the following definition:

struct Thing {
    int foo[256];
    int bar[256];
};

If you now try to access baz you’ll get a segmentation fault, even though the other members work fine.

(edit: added text from “if you get a segfault” to end of answer)