OpenGL Shader Compile Error

Question

I'm having a bit of a problem with my code for compiling shaders, namely they both register as failed compiles and no log is received.

This is the shader compiling code:

/* Make the shader */ Uint size; GLchar* file; loadFileRaw(filePath, file, &size); const char * pFile = file; const GLint pSize = size; newCashe.shader = glCreateShader(shaderType); glShaderSource(newCashe.shader, 1, &pFile, &pSize); glCompileShader(newCashe.shader); GLint shaderCompiled; glGetShaderiv(newCashe.shader, GL_COMPILE_STATUS, &shaderCompiled); if(shaderCompiled == GL_FALSE) { ReportFiler->makeReport("ShaderCasher.cpp", "loadShader()", "Shader did not compile", "The shader " + filePath + " failed to compile, reporting the error - " + OpenGLServices::getShaderLog(newCashe.shader)); }

And these are the support functions:

bool loadFileRaw(string fileName, char* data, Uint* size) { if (fileName != "") { FILE *file = fopen(fileName.c_str(), "rt"); if (file != NULL) { fseek(file, 0, SEEK_END); *size = ftell(file); rewind(file); if (*size > 0) { data = (char*)malloc(sizeof(char) * (*size + 1)); *size = fread(data, sizeof(char), *size, file); data[*size] = '\0'; } fclose(file); } } return data; } string OpenGLServices::getShaderLog(GLuint obj) { int infologLength = 0; int charsWritten = 0; char *infoLog; glGetShaderiv(obj, GL_INFO_LOG_LENGTH,&infologLength); if (infologLength > 0) { infoLog = (char *)malloc(infologLength); glGetShaderInfoLog(obj, infologLength, &charsWritten, infoLog); string log = infoLog; free(infoLog); return log; } return "<Blank Log>"; }

and the shaders I'm loading:

void main(void) { gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0); } void main(void) { gl_Position = ftransform(); }

In short I get

From: ShaderCasher.cpp, In: loadShader(), Subject: Shader did not compile Message: The shader Data/Shaders/Standard/standard.vs failed to compile, reporting the error - <Blank Log>

for every shader I compile.

I've tried replacing the file reading with just a hard coded string but I get the same error so there must be something wrong with how I'm compiling them. I have run and compiled example programs with shaders, so I doubt my drivers are the issue, but in any case I'm on a Nvidia 8600m GT.

Can anyone help?

It's not an exact duplicate, but you might find this answer helpful: stackoverflow.com/questions/2795044/… — Jerry Coffin
– Jerry Coffin, Commented May 27, 2010 at 17:24
are you free() -ing your data anywhere after loadFileRaw()? Unless I'm missing something, I see a memory leak. — Xavier Ho
– Xavier Ho, Commented May 28, 2010 at 10:23
I was planning to cache or display the shader source code somewhere if the compiling fails, but I don't currently have a logger sophisticated enough to do that in a format which is easy to read. I was aware of needing to free the data though, but once that test compile fails you toss all other things aside to find the problem. — Tomas
– Tomas, Commented May 28, 2010 at 15:44

Jesse Beder · Accepted Answer · 2010-05-27 18:39:42Z

In loadFileRaw, you pass char *data by value. Then you assign to it:

data = (char*)malloc(sizeof(char) * (*size + 1));

so your call

loadFileRaw(filePath, file, &size);

does not change the value of file! To change file, pass it in by pointer:

loadFileRaw(filePath, &file, &size);

and then change your function to

bool loadFileRaw(string fileName, char** data, Uint* size) { ... }

and in it,

*data = (char*)malloc(sizeof(char) * (*size + 1));

etc. (for the remaining references to data).

That said, since you're using C++, look into using std::vector<char> or std::string for your memory management. To get you started,

{ std::vector<char> data; data.resize(100); // now it has 100 entries, initialized to zero silly_C_function_that_takes_a_char_pointer_and_a_size(&data[0], 100); // OK } // presto, memory freed

Also, you can look into using std::ifstream for reading files, instead of using FILE *.

My original function used std::ifstream, but I copied the one shown off the internet once I had this problem. Urgh, now I'm getting bad access on glShaderSource
If I make the read function use std::string, won't it need to use chars for the ifstream functions anyway?
@Tomas, I don't follow your second question, but it looks like you're having some trouble with pointers, so why don't you put shaders on hold for a moment and carefully work some simpler examples with pointers (including, but not only, C-style strings) until you feel more comfortable.
I changed my function into one which used strings instead and everything working fine - thanks for the advice. What I was trying to say one comment up was that since fstream's functions all take pointers to chars to send data back, getting it in that form then converting it to a string, only to convert it back for opengl seemed a bit redundant. In any case I found a workaround in an article somewhere which used stringstream and reader->rdbuf() - it seems like a waste of time, but hey, it works. Cheers for the advice and all

Dr. Snoopy · Accepted Answer · 2010-05-27 17:46:10Z

Try with:

glShaderSource(newCashe.shader, 1, &pFile, NULL);

Which is the most commonly used call to load shader sources.

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