Files
mesa/src/glsl/glcpp
Carl Worth c96b8302a3 glsl: glcpp: Allow "#if undefined-macro' to evaluate to false.
A strict reading of the GLSL specification would have this be an
error, but we've received reports from users who expect the
preprocessor to interepret undefined macros as 0. This is the standard
behavior of the rpeprocessor for C, and according to these user
reports is also the behavior of other OpenGL implementations.

So here's one of those cases where we can make our users happier by
ignoring the specification. And it's hard to imagine users who really,
really want to see an error for this case.

The two affected tests cases are updated to reflect the new behavior.

Signed-off-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
2012-06-26 15:20:03 -07:00
..
2012-06-08 11:18:55 -07:00

glcpp -- GLSL "C" preprocessor

This is a simple preprocessor designed to provide the preprocessing
needs of the GLSL language. The requirements for this preprocessor are
specified in the GLSL 1.30 specification availble from:

http://www.opengl.org/registry/doc/GLSLangSpec.Full.1.30.10.pdf

This specification is not precise on some semantics, (for example,
#define and #if), defining these merely "as is standard for C++
preprocessors". To fill in these details, I've been using a draft of
the C99 standard as available from:

http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

Any downstream compiler accepting output from glcpp should be prepared
to encounter and deal with the following preprocessor macros:

	#line
	#pragma
	#extension

All other macros will be handles according to the GLSL specification
and will not appear in the output.

Known limitations
-----------------
The __LINE__ and __FILE__ macros are not yet supported.

A file that ends with a function-like macro name as the last
non-whitespace token will result in a parse error, (where it should be
passed through as is).