GLGETERROR() MachTen Programmer’s Manual GLGETERROR()

NAME
glGetError - return error information

C SPECIFICATION
GLenum glGetError( void )

DESCRIPTION
glGetError returns the value of the error flag. Each
detectable error is assigned a numeric code and symbolic
name. When an error occurs, the error flag is set to the
appropriate error code value. No other errors are
recorded until glGetError is called, the error code is
returned, and the flag is reset to GL_NO_ERROR. If a call
to glGetError returns GL_NO_ERROR, there has been no
detectable error since the last call to glGetError, or
since the GL was initialized.

To allow for distributed implementations, there may be
several error flags. If any single error flag has
recorded an error, the value of that flag is returned and
that flag is reset to GL_NO_ERROR when glGetError is
called. If more than one flag has recorded an error,
glGetError returns and clears an arbitrary error flag
value. Thus, glGetError should always be called in a
loop, until it returns GL_NO_ERROR, if all error flags are
to be reset.

Initially, all error flags are set to GL_NO_ERROR.

The following errors are currently defined:

GL_NO_ERROR No error has been recorded.
The value of this symbolic
constant is guaranteed to be
0.

GL_INVALID_ENUM An unacceptable value is
specified for an enumerated
argument. The offending
command is ignored, and has
no other side effect than to
set the error flag.

GL_INVALID_VALUE A numeric argument is out of
range. The offending com-
mand is ignored, and has no
other side effect than to
set the error flag.

GL_INVALID_OPERATION The specified operation is
not allowed in the current
state. The offending com-
mand is ignored, and has no
other side effect than to
set the error flag.

GL_STACK_OVERFLOW This command would cause a
stack overflow. The
offending command is
ignored, and has no other
side effect than to set the
error flag.

GL_STACK_UNDERFLOW This command would cause a
stack underflow. The
offending command is
ignored, and has no other
side effect than to set the
error flag.

GL_OUT_OF_MEMORY There is not enough memory
left to execute the command.
The state of the GL is unde-
fined, except for the state
of the error flags, after
this error is recorded.

When an error flag is set, results of a GL operation are
undefined only if GL_OUT_OF_MEMORY has occurred. In all
other cases, the command generating the error is ignored
and has no effect on the GL state or frame buffer con-
tents. If the generating command returns a value, it
returns 0. If glGetError itself generates an error, it
returns 0.

ERRORS
GL_INVALID_OPERATION is generated if glGetError is exe-
cuted between the execution of glBegin and the correspond-
ing execution of glEnd. In this case glGetError returns
0.

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