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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
}

API Version Support

OpenGL ES API Version
Function Name 2.0 3.0 3.1
glGetShaderInfoLog
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