<div class="refentry"><a id="glLinkProgram"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glLinkProgram — link a program object</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <strong class="fsfunc">glLinkProgram</strong>(</code></td><td>GLuint <var class="pdparam">program</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>program</code></em></span></dt><dd><p>Specifies the handle of the program object to be linked.</p></dd></dl></div></div><div class="refsect1"><a id="description"></a><h2>Description</h2><p><code class="function">glLinkProgram</code> links the program

object specified by <em class="parameter"><code>program</code></em>. A shader object

of type <code class="constant">GL_VERTEX_SHADER</code> attached to

<em class="parameter"><code>program</code></em> is used to

create an executable that will run on the programmable vertex

processor. A shader object of type <code class="constant">GL_FRAGMENT_SHADER</code>

attached to <em class="parameter"><code>program</code></em> is used to create an

executable that will run on the programmable fragment

processor.</p><p>The status of the link operation will be stored as part of

the program object's state. This value will be set to

<code class="constant">GL_TRUE</code> if the program object was linked

without errors and is ready for use, and

<code class="constant">GL_FALSE</code> otherwise. It can be queried by

calling

<a class="citerefentry" href="glGetProgramiv"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</span></span></a>

with arguments <em class="parameter"><code>program</code></em> and

<code class="constant">GL_LINK_STATUS</code>.</p><p>As a result of a successful link operation, all active

user-defined uniform variables belonging to

<em class="parameter"><code>program</code></em> 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

<a class="citerefentry" href="glGetUniformLocation"><span class="citerefentry"><span class="refentrytitle">glGetUniformLocation</span></span></a>.

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.</p><p>Linking of a program object can fail for a number of

reasons as specified in the <span class="emphasis"><em>OpenGL ES Shading Language

Specification</em></span>. The following lists some of the

conditions that will cause a link error.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A vertex shader and a fragment shader are not both

present in the program object.</p></li><li class="listitem"><p>The number of active attribute variables supported

by the implementation has been exceeded.</p></li><li class="listitem"><p>The storage limit for uniform variables has been

exceeded.</p></li><li class="listitem"><p>The number of active uniform variables supported

by the implementation has been exceeded.</p></li><li class="listitem"><p>The <code class="function">main</code> function is missing

for the vertex shader or the fragment shader.</p></li><li class="listitem"><p>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.</p></li><li class="listitem"><p>A reference to a function or variable name is

unresolved.</p></li><li class="listitem"><p>A shared global is declared with two different

types or two different initial values.</p></li><li class="listitem"><p>One or more of the attached shader objects has not

been successfully compiled (via <a class="citerefentry" href="glCompileShader"><span class="citerefentry"><span class="refentrytitle">glCompileShader</span></span></a>)

or loaded with a pre-compiled shader binary (via <a class="citerefentry" href="glShaderBinary"><span class="citerefentry"><span class="refentrytitle">glShaderBinary</span></span></a>).</p></li><li class="listitem"><p>Binding a generic attribute matrix caused some

rows of the matrix to fall outside the allowed maximum

of <code class="constant">GL_MAX_VERTEX_ATTRIBS</code>.</p></li><li class="listitem"><p>Not enough contiguous vertex attribute slots could

be found to bind attribute matrices.</p></li></ul></div><p>When a program object has been successfully linked, the

program object can be made part of current state by calling

<a class="citerefentry" href="glUseProgram"><span class="citerefentry"><span class="refentrytitle">glUseProgram</span></span></a>.

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

<a class="citerefentry" href="glGetProgramInfoLog"><span class="citerefentry"><span class="refentrytitle">glGetProgramInfoLog</span></span></a>.</p><p><code class="function">glLinkProgram</code> 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

<a class="citerefentry" href="glUseProgram"><span class="citerefentry"><span class="refentrytitle">glUseProgram</span></span></a>.

If the program object currently in use is relinked

unsuccessfully, its link status will be set to

<code class="constant">GL_FALSE</code> , but the executables and

associated state will remain part of the current state until a

subsequent call to <code class="function">glUseProgram</code> removes it

from use. After it is removed from use, it cannot be made part

of current state until it has been successfully relinked.</p><p>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.</p></div><div class="refsect1"><a id="notes"></a><h2>Notes</h2><p>If the link operation is unsuccessful, any information about a previous link operation on <em class="parameter"><code>program</code></em>

is lost (i.e., a failed link does not restore the old state of <em class="parameter"><code>program</code></em>).

Certain information can still be retrieved from <em class="parameter"><code>program</code></em>

even after an unsuccessful link operation. See for instance <a class="citerefentry" href="glGetActiveAttrib"><span class="citerefentry"><span class="refentrytitle">glGetActiveAttrib</span></span></a>

and <a class="citerefentry" href="glGetActiveUniform"><span class="citerefentry"><span class="refentrytitle">glGetActiveUniform</span></span></a>.</p></div><div class="refsect1"><a id="errors"></a><h2>Errors</h2><p><code class="constant">GL_INVALID_VALUE</code>

is generated if <em class="parameter"><code>program</code></em>

is not a value generated by OpenGL.</p><p><code class="constant">GL_INVALID_OPERATION</code>

is generated if <em class="parameter"><code>program</code></em>

is not a program object.</p></div><div class="refsect1"><a id="associatedgets"></a><h2>Associated Gets</h2><p><a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>

with the argument <code class="constant">GL_CURRENT_PROGRAM</code></p><p><a class="citerefentry" href="glGetActiveAttrib"><span class="citerefentry"><span class="refentrytitle">glGetActiveAttrib</span></span></a>

with argument <em class="parameter"><code>program</code></em>

and the index of an active attribute variable</p><p><a class="citerefentry" href="glGetActiveUniform"><span class="citerefentry"><span class="refentrytitle">glGetActiveUniform</span></span></a>

with argument <em class="parameter"><code>program</code></em>

and the index of an active uniform variable<em class="parameter"><code></code></em></p><p><a class="citerefentry" href="glGetAttachedShaders"><span class="citerefentry"><span class="refentrytitle">glGetAttachedShaders</span></span></a>

with argument <em class="parameter"><code>program</code></em></p><p><a class="citerefentry" href="glGetAttribLocation"><span class="citerefentry"><span class="refentrytitle">glGetAttribLocation</span></span></a>

with argument <em class="parameter"><code>program</code></em>

and an attribute variable name</p><p><a class="citerefentry" href="glGetProgramiv"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</span></span></a>

with arguments <em class="parameter"><code>program</code></em>

and <code class="constant">GL_LINK_STATUS</code></p><p><a class="citerefentry" href="glGetProgramInfoLog"><span class="citerefentry"><span class="refentrytitle">glGetProgramInfoLog</span></span></a>

with argument <em class="parameter"><code>program</code></em></p><p><a class="citerefentry" href="glGetUniform"><span class="citerefentry"><span class="refentrytitle">glGetUniform</span></span></a>

with argument <em class="parameter"><code>program</code></em>

and a uniform variable location</p><p><a class="citerefentry" href="glGetUniformLocation"><span class="citerefentry"><span class="refentrytitle">glGetUniformLocation</span></span></a>

with argument <em class="parameter"><code>program</code></em>

and a uniform variable name</p><p><a class="citerefentry" href="glIsProgram"><span class="citerefentry"><span class="refentrytitle">glIsProgram</span></span></a></p></div>

{$pipelinestall}{$examples}

<div class="refsect1"><a id="seealso"></a><h2>See Also</h2><p><a class="citerefentry" href="glAttachShader"><span class="citerefentry"><span class="refentrytitle">glAttachShader</span></span></a>,

<a class="citerefentry" href="glBindAttribLocation"><span class="citerefentry"><span class="refentrytitle">glBindAttribLocation</span></span></a>,

<a class="citerefentry" href="glCompileShader"><span class="citerefentry"><span class="refentrytitle">glCompileShader</span></span></a>,

<a class="citerefentry" href="glShaderBinary"><span class="citerefentry"><span class="refentrytitle">glShaderBinary</span></span></a>,

<a class="citerefentry" href="glCreateProgram"><span class="citerefentry"><span class="refentrytitle">glCreateProgram</span></span></a>,

<a class="citerefentry" href="glDeleteProgram"><span class="citerefentry"><span class="refentrytitle">glDeleteProgram</span></span></a>,

<a class="citerefentry" href="glDetachShader"><span class="citerefentry"><span class="refentrytitle">glDetachShader</span></span></a>,

<a class="citerefentry" href="glUniform"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a>,

<a class="citerefentry" href="glUseProgram"><span class="citerefentry"><span class="refentrytitle">glUseProgram</span></span></a>,

<a class="citerefentry" href="glValidateProgram"><span class="citerefentry"><span class="refentrytitle">glValidateProgram</span></span></a></p></div><div class="refsect1"><div id="Copyright"><h2>Copyright</h2><p>

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.

<a class="ulink" href="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.

</p></div></div></div>