basic c pointer returning - c++

Question

The following app crashes with nullpointer. I am wondering whats wrong...
#include "stdio.h"
#include "string.h"
char* getFileData(char* fileName);
bool createShader( int shaderType, const char* shader, const char* shaderFile ) ;
void glShaderSource(int shader, int count, const char** string, const int* length);
int main(int argc, char* argv[])
{
char* shader = getFileData("filea.csd");
bool success = createShader(1, shader, "filea.csd");
return 0;
}
char* getFileData(char* fileName) {
if(!strcmp(fileName, "filea.csd"))
return "this is the content of the file a\0";
else if(!strcmp(fileName, "fileb.csd"))
return "this is the content of the file b\0";
else if(!strcmp(fileName, "filec.csd"))
return "this is the content of the file c\0";
else
return "";
}
bool createShader( int shaderType, const char* shader, const char* shaderFile )
{
int shaderHandle = 122;
glShaderSource( shaderHandle, 1, &shader, NULL ); ////This line is where it crashes.
return true;
}
void glShaderSource(int shader, int count, const char** string, const int* length) {
}

Answer 1

Since the Pointer is NULL, try passing the double pointer. Something of the form
bool createShader( GLenum shaderType, const char** shader, const char* shaderFile )//<-- change
{
GLuint shaderHandle = glCreateShader( shaderType );
glShaderSource( shaderHandle, 1, shader, NULL ); //<--change
glCompileShader( shaderHandle );
int status = 0;
glGetShaderiv( shaderHandle, GL_COMPILE_STATUS, &status );
}
void main () {
char* shader = strdup(getFileData("filea.csd"));
bool success = createShader(shaderType, &shader, "filea.csd"); //<--change
delete shader;
return success;
}

Answer 2

I think checking the return value from glCreateShader might be a good thing. Make sure it's non-zero.
The line
delete shader
is also wrong. It may not be crashing there but you need to use free to release memory allocated by malloc.

Answer 3

One bug I see is this line:
delete shader;
That line will only work correctly if the memory pointed by shader was allocated with the new operator. But if we look at your getFileData() method, we see that the character arrays it returns are not allocated by new, but rather are static data.
So the fix would be to have getFileData() return a character array that was allocated by the new operator, or better yet a std::string. Using dynamically-allocated character arrays for string handling is very error prone and not recommended.