spec - OpenGL

2.14. VERTEX SHADERS 107
LINK_STATUS is FALSE, its program binary length is zero, and a call to GetProgramBinary
will generate an INVALID_OPERATION error.
The command
void ProgramBinary( uint program, enum binaryFormat,
const void *binary, sizei length );
loads a program object with a program binary previously returned from GetProgramBinary.
This is useful for future instantiations of the GL to avoid online compilation,
while still using OpenGL Shading Language source shaders as a portable
initial format. binaryFormat and binary must be those returned by a previous
call to GetProgramBinary, and length must be the length of the program binary
as returned by GetProgramBinary or GetProgramiv with pname PROGRAM_-
BINARY_LENGTH. The program binary will fail, setting the LINK_STATUS of program
to FALSE, if these conditions are not met.
A program binary may also fail if the implementation determines that there has
been a change in hardware or software configuration from when the program binary
was produced such as having been compiled with an incompatible or outdated
version of the compiler. In this case the application should fall back to providing
the original OpenGL Shading Language source shaders, and perhaps again retrieve
the program binary for future use.
A program object’s program binary is replaced by calls to LinkProgram or
ProgramBinary. Where linking success or failure is concerned, ProgramBinary
can be considered to perform an implicit linking operation. LinkProgram and
ProgramBinary both set the program object’s LINK_STATUS to TRUE or FALSE,
as queried with GetProgramiv, to reflect success or failure and update the information
log, queried with GetProgramInfoLog, to provide details about warnings
or errors.
A successful call to ProgramBinary will reset all uniform variables to their
initial values. The initial value is either the value of the variable’s initializer as
specified in the original shader source, or zero if no initializer was present.
Additionally, all vertex shader input and fragment shader output assignments
that were in effect when the program was linked before saving are restored when
ProgramBinary is called.
If ProgramBinary failed, any information about a previous link or load of that
program object is lost. Thus, a failed load does not restore the old state of program.
The failure does not alter other program state not affected by linking such as the
attached shaders, and the vertex attribute and fragment data location bindings as
set by BindAttribLocation and BindFragDataLocation.
Queries of values NUM_PROGRAM_BINARY_FORMATS and PROGRAM_-
BINARY_FORMATS return the number of program binary formats and the list of
OpenGL 4.2 (Compatibility Profile) - August 22, 2011