variable-length-array

Based on a comment of someone in another thread: VLAs introduce more problems than they solve, because you never know if the declaration is going to crash for x being too large for the stack. This code will overflow because sizeof(a) is too long for the stack: #include <stdio.h> #include <stdlib.h> int main(void) { int n = 100000000; int a[4][n]; printf("%zu\n", sizeof(a)); return 0; } But this one can not because sizeof(a) is 8 (the size of a pointer in my computer): #include <stdio.h> #include <stdlib.h> int main(void) { int n = 100000000; int (*a)[n]; printf("%zu\n", sizeof(a)); a = malloc

I've created 2 structures to represent images (a pixel and an image one) in C. typedef struct pixel { unsigned char red; unsigned char green; unsigned char blue; }; typedef struct image { int width; int heigth; struct pixel pixels[width][heigth]; }; I am getting an error saying that width and heigth are not defined in the definition of image. I don't get why I'm getting that error and how I can solve it i would suggest an alternative like this: typedef struct { int width; int heigth; struct pixel *pixels; } image; every time, you need to alloc: image img; /* init */ img.pixels=malloc(sizeof

I'm dynamically calculating the size of an array. Something like: void foo(size_t limit) { char buffer[limit * 14 + 1]; } But just GCC compiler says: error: ISO C90 forbids variable length array ‘buffer’ searching on SO I found this answer : C99 §6.7.5.2: If the size is an expression that is not an integer constant expression... ...each time it is evaluated it shall have a value greater than zero. So, I did the re-declaration of size limit type variable to: void foo(const size_t limit) But it continues to give warning for me. Is this a GCC bug? const -qualifying a variable doesn't make it a

In Visual Studio 2005, I'm trying to compile a .c file: int i = 6; int a[i]; It doesn't work, so which standard does my compiler follow? Visual Studio only supports C89/90. They have no support for C99. Therefore you cannot use variable-length arrays in Visual Studio. Furthermore, Microsoft has no plans to add support for C99 in their C compiler. 来源： https://stackoverflow.com/questions/7871019/variable-length-arrays-c99-not-supported-in-c