Returning strings from function in c

Question

I am confused as to how we are able to return strings from function.

char* someFunction() { return "Hello, World" }

Shouldn't the above return statement throw "function returns address of local variable" and how is it different from the function:

char* newFunction() { char temp[] = "Hello, World"; return temp; }

which in fact does give the warning mentioned above.

Note that the word "throw" often refers to an exception handling mechanism... That's probably not what you meant, given that C does not have any innate support for such. — Kaganar
– Kaganar, Commented Jun 18, 2012 at 17:51
There's an existing question that covers the critical difference between the two cases. — Flexo - Save the data dump
– Flexo - Save the data dump ♦, Commented Jun 18, 2012 at 17:56

TJD · Accepted Answer · 2012-06-18 17:47:40Z

5

In the first case, the string lives in constant readonly memory at a fixed address for all time. In the second case, the string is put locally on the stack, and so is temporary.

answered Jun 18, 2012 at 17:47

TJD

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2 Comments

Pratt Over a year ago

I didn't completely understand what you said. Are you saying that since it is a string constant the compiler would have already allocated memory for it during compile-time and therefore not cause any problem.

TJD Over a year ago

Yes, the compiler is statically allocating the string at a fixed global address. I mean the same thing as the accepted answer from ouah.

ouah · Accepted Answer · 2012-06-18 17:57:50Z

String literals have static storage duration. You can return a pointer to a string and then access the string, it is perfectly valid and defined behavior.

char* someFunction() { return "Hello, World" }

In the below case, you are returning a pointer to a string with automatic storage duration. An object with automatic storage duration is destroyed after exiting the block where it is defined. So accessing it after the function returns is undefined behavior.

char* newFunction() { char temp[] = "Hello, World"; return temp; }

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