strdup dumping core on passing NULL

c linux compiler-construction posix freebsd
hari picture hari · Jun 21, 2011 · Viewed 10.8k times · Source

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.

Answer

nos picture nos · Jun 21, 2011

That's quite ok.

The documentation implies that it's argument must be string, if it's something else, such as a null pointer, it's anyones 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 behavor if you pass them something you're not supposed to. Many standard C function such as strcpy, strlen does not accept null pointers either.

Related questions

How to compile .c file with OpenSSL includes?

I am trying to compile a small .c file that has the following includes: #include <openssl/ssl.h> #include <openssl/rsa.h> #include <openssl/x509.h> #include <openssl/evp.h> In the …

Read More
Why is the .bss segment required?

What I know is that global and static variables are stored in the .data segment, and uninitialized data are in the .bss segment. What I don't understand is why do we have dedicated segment for uninitialized variables? If an uninitialised …

Read More
When / How does Linux load shared libraries into address space?

My question is the following: When is the address of shared objects specified in programs? During linking? Loading? If I wanted to find the memory address of the system command inside of libc inside of my program I could find …

Read More