free

If I would write: char *a=malloc(sizeof(char)*4); a="abc"; char *b="abc"; do I need to free this memory, or is it done by my system? In your situation you won't have any way to free the dynamic allocated memory because you are losing the reference to it. Try this out: #include <stdio.h> #include <stdlib.h> int main() { char *a=(char*)malloc(sizeof(char)*4); printf("Before: %p\n",a); a = "abc"; printf("After: %p\n",a); free(a); char *b = "abc"; return 0; } You will obtain Before: 0x100100080 After: 0x100000f50 You will see that the two pointers are different. This because the string literal

Possible Duplicate: Malloc or normal array definition? We learn that there is dynamic memory in C and dynamic variables: #include <stdio.h> int a = 17; int main(void) { int b = 18; //automatic stack memory int * c; c = malloc( sizeof( int ) ); //dynamic heap memory *c = 19; printf("a = %d at address %x\n", a, &a); printf("b = %d at address %x\n", b, &b); printf("c = %d at address %x\n", *c, c); free(c); system("PAUSE"); return 0; } How do I know which type of memory to use? When do I ned one or the other? Use dynamic in the following situations: When you need a lot of memory. Typical stack

I'm trying to learn C and I'm currently trying to write a basic stack data structure, but I can't seem to get basic malloc / free right. Here's the code I've been using (I'm just posting a small part here to illustrate a specific problem, not the total code, but the error message was generated just by running this example code in valgrind ) #include <stdio.h> #include <stdlib.h> typedef struct Entry { struct Entry *previous; int value; } Entry; void destroyEntry(Entry entry); int main(int argc, char *argv[]) { Entry* apple; apple = malloc(sizeof(Entry)); destroyEntry(*(apple)); return 0; }

I want to generate a Program Dependence Graph (PDG) from C source code. I found papers that explain how do it, but all used the commercial CodeSurfer tool. Are there any free tools or open source projects that can do this job? Pascal Cuoq Frama-C is an Open Source static analysis platform with a slicer for C programs based on the computation of a Program Dependence Graph. Note that slicing actual programs written in a real programming language such as C involves many special cases and concepts that are skimmed over in scientific publications. Still, I am confident that you won't find anything

In C and C++, Freeing a NULL pointer will result in nothing done. Still, I see people saying that memory corruption can occur if you "free memory twice". Is this true? What is going on under the hood when you free memory twice? N 1.1 int *p = malloc(sizeof(int)); //value of p is now lets say 0x12345678 *p = 2; free(p); //memory pointer is freed, but still value of p is 0x12345678 //now, if you free again, you get a crash or undefined behavior. So, after free ing the first time, you should do p = NULL , so if (by any chance), free(p) is called again, nothing will happen. Here is why freeing