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# docs.GL

OpenGL 4
OpenGL 3
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# glGetShaderInfoLog

## Name

glGetShaderInfoLog — Returns the information log for a shader object

## C Specification

`void glGetShaderInfoLog(` | GLuint shader,
| GLsizei maxLength,
| GLsizei *length,
| GLchar *infoLog`)`;

## Parameters

`shader`

  Specifies the shader object whose information log is to be queried.

`maxLength`

  Specifies the size of the character buffer for storing the returned information log.

`length`

  Returns the length of the string returned in `infoLog` (excluding the null terminator).

`infoLog`

  Specifies an array of characters that is used to return the information log.

## Description

`glGetShaderInfoLog` returns the information log for the specified shader object. The information log for a shader object is modified when the shader is compiled. The string that is returned will be null terminated.

`glGetShaderInfoLog` returns in `infoLog` as much of the information log as it can, up to a maximum of `maxLength` characters. The number of characters actually returned, excluding the null termination character, is specified by `length`. If the length of the returned string is not required, a value of `NULL` can be passed in the `length` argument. The size of the buffer required to store the returned information log can be obtained by calling glGetShaderiv with the value `GL_INFO_LOG_LENGTH`.

The information log for a shader object is a string that may contain diagnostic messages, warning messages, and other information about the last compile operation. When a shader object is created, its information log will be a string of length 0.

## Notes

The information log for a shader object is the OpenGL implementer's primary mechanism for conveying information about the compilation process. Therefore, the information log can be helpful to application developers during the development process, even when compilation is successful. Application developers should not expect different OpenGL implementations to produce identical information logs.

## Errors

`GL_INVALID_VALUE` is generated if `shader` is not a value generated by OpenGL.

`GL_INVALID_OPERATION` is generated if `shader` is not a shader object.

`GL_INVALID_VALUE` is generated if `maxLength` is less than 0.

## Associated Gets

glGetShaderiv with argument `GL_INFO_LOG_LENGTH`

glIsShader

## Examples

Compile a program from a vertex shader and a fragment shader.

    GLuint vshader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vshader, 1, &vertex_shader_source, NULL); // vertex_shader_source is a GLchar* containing glsl shader source code
    glCompileShader(vshader);

    GLint vertex_compiled;
    glGetShaderiv(vshader, GL_COMPILE_STATUS, &vertex_compiled);
    if (vertex_compiled != GL_TRUE)
    {
        GLsizei log_length = 0;
        GLchar message[1024];
        glGetShaderInfoLog(vshader, 1024, &log_length, message);
        // Write the error to a log
    }

    GLuint fshader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fshader, 1, &fragment_shader_source, NULL); // fragment_shader_source is a GLchar* containing glsl shader source code
    glCompileShader(fshader);

    GLint fragment_compiled;
    glGetShaderiv(fshader, GL_COMPILE_STATUS, &fragment_compiled);
    if (fragment_compiled != GL_TRUE)
    {
        GLsizei log_length = 0;
        GLchar message[1024];
        glGetShaderInfoLog(fshader, 1024, &log_length, message);
        // Write the error to a log
    }

    GLuint program = glCreateProgram();

    // This step is unnecessary if you use the location specifier in your shader
    // e.g. layout (location = 0) in vec3 position;
    glBindAttribLocation(program, 0, "position"); // The index passed into glBindAttribLocation is
    glBindAttribLocation(program, 1, "texcoord"); // used by glEnableVertexAttribArray. "position"
    glBindAttribLocation(program, 2, "normal");   // "texcoord" "normal" and "color" are the names of the
    glBindAttribLocation(program, 3, "color");    // respective inputs in your fragment shader.

    glAttachShader(program, vshader);
    glAttachShader(program, fshader);
    glLinkProgram(program);

    GLint program_linked;
    glGetProgramiv(program, GL_LINK_STATUS, &program_linked);
    if (program_linked != GL_TRUE)
    {
        GLsizei log_length = 0;
        GLchar message[1024];
        glGetProgramInfoLog(program, 1024, &log_length, message);
        // Write the error to a log
    }

## Tutorials

open.gl - The Graphics Pipeline
opengl-tutorial.org - Tutorial 2 : The first triangle

## API Version Support

| OpenGL ES API Version
--- | ---
Function Name | 2.0 | 3.0 | 3.1
glGetShaderInfoLog | ✔ | ✔ | ✔

## See Also

glCompileShader, glGetProgramInfoLog, glLinkProgram, glValidateProgram

## Copyright

Copyright © 2003-2005 3Dlabs Inc. Ltd. Copyright © 2010-2014 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. https://opencontent.org/openpub/.

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