glLinkProgram man page on Oracle
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GLLINKPROGRAM(3G) OpenGL Manual GLLINKPROGRAM(3G)
NAME
glLinkProgram - Links a program object
C SPECIFICATION
void glLinkProgram(GLuint program);
PARAMETERS
program
Specifies the handle of the program object to be linked.
DESCRIPTION
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_GEOMETRY_SHADER are
attached to program, they will be used to create an executable that
will run on the programmable geometry 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, geometry or 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, or geometry shader shader if present.
· 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.
· The program object contains objects to form a fragment shader but
does not contain objects to form a vertex shader.
· The program object contains objects to form a geometry shader but
does not contain objects to form a vertex shader.
· The program object contains objects to form a geometry shader and
the input primitive type, output primitive type, or maximum output
vertex count is not specified in any compiled geometry shader
object.
· The program object contains objects to form a geometry shader and
the input primitive type, output primitive type, or maximum output
vertex count is specified differently in multiple geometry shader
objects.
· The number of active outputs in the fragment shader is greater than
the value of GL_MAX_DRAW_BUFFERS.
· The program has an active output assigned to a location greater
than or equal to the value of GL_MAX_DUAL_SOURCE_DRAW_BUFFERS and
has an active output assigned an index greater than or equal to
one.
· More than one varying out variable is bound to the same number and
index.
· The explicit binding assigments do not leave enough space for the
linker to automatically assign a location for a varying out array,
which requires multiple contiguous locations.
· The count specified by glTransformFeedbackVaryings() is non-zero,
but the program object has no vertex or geometry shader.
· Any variable name specified to glTransformFeedbackVaryings() in the
varyings array is not declared as an output in the vertex shader
(or the geometry shader, if active).
· Any two entries in the varyings array given
glTransformFeedbackVaryings() specify the same varying variable.
· The total number of components to capture in any transform feedback
varying variable is greater than the constant
GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS and the buffer mode
is SEPARATE_ATTRIBS.
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, and
optionally of type GL_GEOMETRY_SHADER, but does not contain shader
objects of type GL_FRAGMENT_SHADER, the vertex shader executable will
be installed on the programmable vertex processor, the geometry shader
executable, if present, will be installed on the programmable geometry
processor, but no executable will be installed on the fragment
processor. The results of rasterizing primitives with such a program
will be undefined.
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.
NOTES
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().
ERRORS
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 program is the currently active
program object and transform feedback mode is active.
ASSOCIATED GETS
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
glIsProgram()
SEE ALSO
glAttachShader(), glBindAttribLocation(), glCompileShader(),
glCreateProgram(), glDeleteProgram(), glDetachShader(), glUniform(),
glUseProgram(), glValidateProgram()
COPYRIGHT
Copyright © 2003-2005 3Dlabs Inc. Ltd. Copyright © 2010 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.
http://opencontent.org/openpub/.
AUTHORS
opengl.org
opengl.org 04/29/2014 GLLINKPROGRAM(3G)
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