CODEWITHSUNDEEP
clinuxposixfreebsd
hari
hari

Reputation: 9733

strdup dumping core on passing NULL

strdup(null) dumps core.

Tried in on ubuntu and freeBSD both.

why? Shouldn't it return null?

char *b = NULL;
a = strdup(b);

This will dump core on strdup call.

Upvotes: 14

Views: 16115

Answers (4)

nos
nos

Reputation: 229184

That's quite ok.

The documentation implies that its argument must be a string. If it's something else, such as a null pointer, it's anyone's guess what'll happen. In essence, you get undefined behavior when passing a NULL pointer to strdup.

It's quite normal for functions to yield undefined behavior if you pass them something you're not supposed to. Many standard C functions such as strcpy and strlen do not accept null pointers either.

Upvotes: 26

Ben Voigt
Ben Voigt

Reputation: 283733

strdup returns NULL in case of allocation failure.

This is not allocation failure. The behavior when a wild pointer is passed in is undefined. You're required to pass in a valid pointer to a NUL-terminated string.

Upvotes: 8

Kai Petzke
Kai Petzke

Reputation: 2984

Of course, all the answers are correct. Nonetheless, in case of strdup(), it would be nice to have it to be able to deal with null pointers, too - just return a "null" string too, in that case. Of course, it is easy to define a strdupnullok() function with that behaviour as a wrapper around strdup(), but it is then an additional wrapper and function call, so makes code a tiny bit slower.

Upvotes: 2

UncleAli
UncleAli

Reputation: 505

I think that it is expected behaviour.

Upvotes: 2

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