_glGetError: return error information
FUNCTION _glGetError~& GLenum _glGetError(void);
_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:
- No error has been recorded. The value of this symbolic constant is guaranteed to be 0.
- 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.
- A numeric argument is out of range. The offending command is ignored and has no other side effect than to set the error flag.
- 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.
- The framebuffer object is not complete. The offending command is ignored and has no other side effect than to set the error flag.
- 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.
- An attempt has been made to perform an operation that would cause an internal stack to underflow.
- An attempt has been made to perform an operation that would cause an internal stack to overflow.
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.
Copyright 1991-2006 Silicon Graphics, Inc. Copyright 2012 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.