glGetShaderiv — return a parameter from a shader object
void glGetShaderiv( | GLuint shader, |
| GLenum pname, | |
GLint *params); |
shaderSpecifies the shader object to be queried.
pnameSpecifies the object parameter. Accepted symbolic names are GL_SHADER_TYPE, GL_DELETE_STATUS, GL_COMPILE_STATUS, GL_INFO_LOG_LENGTH, GL_SHADER_SOURCE_LENGTH.
paramsReturns the requested object parameter.
glGetShaderiv returns in params the value of a parameter for a specific shader object. The following parameters are defined:
GL_SHADER_TYPE params returns GL_VERTEX_SHADER if shader is a vertex shader object, and GL_FRAGMENT_SHADER if shader is a fragment shader object.
GL_DELETE_STATUS params returns GL_TRUE if shader is currently flagged for deletion, and GL_FALSE otherwise.
GL_COMPILE_STATUSFor implementations that support a shader compiler, params returns GL_TRUE if the last compile operation on shader was successful, and GL_FALSE otherwise.
GL_INFO_LOG_LENGTHFor implementations that support a shader compiler, params returns the number of characters in the information log for shader including the null termination character (i.e., the size of the character buffer required to store the information log). If shader has no information log, a value of 0 is returned.
GL_SHADER_SOURCE_LENGTHFor implementations that support a shader compiler, params returns the length of the concatenation of the source strings that make up the shader source for the shader, including the null termination character. (i.e., the size of the character buffer required to store the shader source). If no source code exists, 0 is returned.
Shader compiler support is optional, and thus must be queried before use by calling glGet with argument GL_SHADER_COMPILER. glShaderSource, glCompileShader, glGetShaderPrecisionFormat, and glReleaseShaderCompiler will each generate GL_INVALID_OPERATION on implementations that do not support a shader compiler, as will glGetShaderiv queries of GL_COMPILE_STATUS, GL_INFO_LOG_LENGTH, and GL_SHADER_SOURCE_LENGTH. Such implementations instead offer the glShaderBinary alternative for supplying a pre-compiled shader binary.
If an error is generated, no change is made to the contents of params.
GL_INVALID_ENUM is generated if pname is not an accepted value.
GL_INVALID_VALUE is generated if shader is not a value generated by OpenGL.
GL_INVALID_OPERATION is generated if pname is GL_COMPILE_STATUS, GL_INFO_LOG_LENGTH, or GL_SHADER_SOURCE_LENGTH but a shader compiler is not supported.
GL_INVALID_OPERATION is generated if shader does not refer to a shader object.
glGet with argument GL_SHADER_COMPILER
glGetShaderInfoLog with argument shader
glGetShaderSource with argument 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 }
glCompileShader, glCreateShader, glDeleteShader, glGetProgramiv, glShaderSource, glShaderBinary
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