Undefined reference to memcpy_s

Question

I'm trying to fix an undefined reference to memcpy_s() error. I've included string.h in my file and the memcpy() function works okay, and I've also tried including memory.h. I'm on x64 Windows 7 and using gcc 4.8.1 to compile.

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

void doMemCopy(char* buf, size_t buf_size, char* in, int chr) {
    memcpy_s(buf, buf_size, in, chr);
}

memory for buf has been allocated in the main function, which calls doMemCpy(buf, 64, in, bytes). in is a string read from standard input

Exact error from cmd terminal:

undefined reference to "memcpy_s" collect2.exe: error: ld returned 1 exit status

Hydraulics

have both buf and in been allocated? What is the exact error you get? Show the context where you call the function – Septicidal

buf has been allocated in the main() function, and in is a string read from standard input. The error I got was undefined reference to "memcpy_s" collect2.exe: error: ld returned 1 exit status – Hydraulics

new information should be added to the question. please add the info from your comment to your question. – Ackley

@Ackley not required. It is unrelated to the actual question. – Therine

is it trying to link to a wrong version? – Acetylate

Answer 1

GCC 4.8 does not include the function memcpy_s, or any of the other _s bounds checking functions as far as I can tell. These functions are defined in ISO 9899:2011 Annex K and they are optional to implement. Before using them you must check if __STDC_LIB_EXT1__ is defined.

These functions were originally implemented by Microsoft and many parties objected to including them in the standard. I think the main objection is that the error handling that is done by the functions involves a global callback handle that is shared between threads, but they are also quite inefficient.

Further reading is available from Carlos O'Donell and Martin Sebor in Updated Field Experience With Annex K — Bounds Checking Interfaces.

Automat

Answer 2

I've never used this, but AFAIK, you need to add

#define __STDC_WANT_LIB_EXT1__ 1

before

#include <string.h>

to use memcpy_s().

Therine

Would this also require a -std=c11 compile option? – Murraymurre

Nope. That's for C11. – End

@FredLarson it seems so from the reference that you provided. memcpy_s is since c11. – Rayleigh

Quoting from the above reference, As all bounds-checked functions, memcpy_s is only guaranteed to be available if STDC_LIB_EXT1 is defined by the implementation and if the user defines STDC_WANT_LIB_EXT1 to the integer constant 1 before including string.h. the definition that you stated should be before the line #include <string.h> – Rayleigh

@RakholiyaJenish: I'd probably define that on the compile line too: -DSTDC_WANT_LIB_EXT1=1 – Murraymurre

I included #define __STDC_WANT_LIB_EXT1__ 1 before #include <string.h> and I'm still getting the same error. When I try compiling it with -std=c11 I get warning: implicit declaration of function "memcpy_s" [-Wimplicit-function-declaration] in addition to the undefined reference error – Hydraulics

I don't have access to the same compiler, but it seems unlikely that the error has anything to do with headers, defines or even compilation since this is a link time error indicating that it is missing from the library (possibly because it was not compiled to support it). Unless of course memcpy_s() is a static inline function or macro. – Meristic