glGetError(3G)

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 command is ignored, and has no
                                   other side effect than to set the error
                                   flag. This flag is also set when the
                                   implementation cannot accomodate an image
                                   of the size requested by glTexImage3DExt,
                                   glTexImage2D, or glTexImage1D.  The error
                                   is  not generated for a
                                   GL_PROXY_TEXTURE_3D_EXT, a
                                   GL_PROXY_TEXTURE_2D_EXT, or a
                                   GL_PROXY_TEXTURE_1D_EXT.
     GL_INVALID_OPERATION          The specified operation is not allowed in
                                   the current state.  The offending command
                                   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
                                   undefined, except for the state of the
                                   error flags, after this error is recorded.

     GL_TABLE_TOO_LARGE_EXT        The implementation cannot accomodate a
                                   table of the size requested by
                                   glHistogramEXT.  The error is not generated
                                   for GL_PROXY_HISTOGRAM_EXT.

     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 contents.  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 executed between the
     execution of glBegin and the corresponding execution of glEnd.  In this
     case glGetError returns 0.