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glLinkProgram — Links a program object
void glLinkProgram(GLuint program);
glLinkProgram links the program
object specified by program. If any
shader objects of type GL_VERTEX_SHADER are
attached to program, they will be used to
create an executable that will run on the programmable vertex
processor. If any shader objects of type
GL_FRAGMENT_SHADER are attached to
program, they will be used to create an
executable that will run on the programmable fragment
processor.
The status of the link operation will be stored as part of
the program object's state. This value will be set to
GL_TRUE if the program object was linked
without errors and is ready for use, and
GL_FALSE otherwise. It can be queried by
calling
glGetProgram
with arguments program and
GL_LINK_STATUS.
As a result of a successful link operation, all active
user-defined uniform variables belonging to
program will be initialized to 0, and
each of the program object's active uniform variables will be
assigned a location that can be queried by calling
glGetUniformLocation.
Also, any active user-defined attribute variables that have not
been bound to a generic vertex attribute index will be bound to
one at this time.
Linking of a program object can fail for a number of reasons as specified in the OpenGL Shading Language Specification. The following lists some of the conditions that will cause a link error.
The number of active attribute variables supported by the implementation has been exceeded.
The storage limit for uniform variables has been exceeded.
The number of active uniform variables supported by the implementation has been exceeded.
The main function is missing
for the vertex shader or the fragment shader.
A varying variable actually used in the fragment shader is not declared in the same way (or is not declared at all) in the vertex shader.
A reference to a function or variable name is unresolved.
A shared global is declared with two different types or two different initial values.
One or more of the attached shader objects has not been successfully compiled.
Binding a generic attribute matrix caused some
rows of the matrix to fall outside the allowed maximum
of GL_MAX_VERTEX_ATTRIBS.
Not enough contiguous vertex attribute slots could be found to bind attribute matrices.
When a program object has been successfully linked, the program object can be made part of current state by calling glUseProgram. Whether or not the link operation was successful, the program object's information log will be overwritten. The information log can be retrieved by calling glGetProgramInfoLog.
glLinkProgram will also install the
generated executables as part of the current rendering state if
the link operation was successful and the specified program
object is already currently in use as a result of a previous
call to
glUseProgram.
If the program object currently in use is relinked
unsuccessfully, its link status will be set to
GL_FALSE , but the executables and
associated state will remain part of the current state until a
subsequent call to glUseProgram removes it
from use. After it is removed from use, it cannot be made part
of current state until it has been successfully relinked.
If program contains shader objects
of type GL_VERTEX_SHADER but does not
contain shader objects of type
GL_FRAGMENT_SHADER, the vertex shader will
be linked against the implicit interface for fixed functionality
fragment processing. Similarly, if
program contains shader objects of type
GL_FRAGMENT_SHADER but it does not contain
shader objects of type GL_VERTEX_SHADER,
the fragment shader will be linked against the implicit
interface for fixed functionality vertex processing.
The program object's information log is updated and the program is generated at the time of the link operation. After the link operation, applications are free to modify attached shader objects, compile attached shader objects, detach shader objects, delete shader objects, and attach additional shader objects. None of these operations affects the information log or the program that is part of the program object.
glLinkProgram
is available only if the GL version is 2.0 or greater.
If the link operation is unsuccessful, any information about a previous link operation on program
is lost (i.e., a failed link does not restore the old state of program
). Certain information can still be retrieved from program
even after an unsuccessful link operation. See for instance glGetActiveAttrib
and glGetActiveUniform.
GL_INVALID_VALUE
is generated if program
is not a value generated by OpenGL.
GL_INVALID_OPERATION
is generated if program
is not a program object.
GL_INVALID_OPERATION
is generated if glLinkProgram
is executed between the execution of glBegin
and the corresponding execution of glEnd.
glGet
with the argument GL_CURRENT_PROGRAM
glGetActiveAttrib
with argument program
and the index of an active attribute variable
glGetActiveUniform
with argument program
and the index of an active uniform variable
glGetAttachedShaders
with argument program
glGetAttribLocation
with argument program
and an attribute variable name
glGetProgram
with arguments program
and GL_LINK_STATUS
glGetProgramInfoLog
with argument program
glGetUniform
with argument program
and a uniform variable location
glGetUniformLocation
with argument program
and a uniform variable name
glAttachShader, glBindAttribLocation, glCompileShader, glCreateProgram, glDeleteProgram, glDetachShader, glUniform, glUseProgram, glValidateProgram
Copyright © 2003-2005 3Dlabs Inc. Ltd. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.