GLSL #if directive with ==

问题

Some people are reporting bugs in shaders in our client software. Reports looks like this:

ERROR: 0:63: error#71) Syntax error incorrect preprocessor directive
WARNING: 0:63: warning#64) Unexpected tokens following the preprocessor directive - expected a newline(#if )
ERROR: 0:67: error#71) Syntax error incorrect preprocessor directive
WARNING: 0:67: warning#64) Unexpected tokens following the preprocessor directive - expected a newline(#if )
ERROR: 0:71: error#71) Syntax error incorrect preprocessor directive
WARNING: 0:71: warning#64) Unexpected tokens following the preprocessor directive - expected a newline(#if )
ERROR: 0:75: error#71) Syntax error incorrect preprocessor directive
WARNING: 0:75: warning#64) Unexpected tokens following the preprocessor directive - expected a newline(#if )

And more. Every error is on line like this:

#if ATLAS_MAG_MIN_FILTER == 7 // Here goes the comment

We tried changing all these ifs to the following format:

#if (ATLAS_MAG_MIN_FILTER == 7) // Comment

But the error is still occurring. I cant find any documentation on the way we should write #ifs in GLSL. Can anybody tell me how to use them correctly?

Added: ATLAS_MAG_MIN_FILTER is defined as:

#define ATLAS_MAG_MIN_FILTER (ATLAS_FILTER_MODE & 0x7)

ATLAS_FILTER_MODE is defined as:

#define ATLAS_FILTER_MODE 5

All newlines are in place.

There are errors on lines without comments too.

I uploaded full code of the shader here, errors occurred on lines 63, 67, 71, 75, 79, 83, 87, 91, 111, 114, 115, 122, 125, 126.

回答1:

I found the problem: hex constants are not allowed in some implementations. Tested on ATI Radeon HD 4800 Series with driver version 8.17.10.1129.

I used this code as test:

#define TESTVAR_1 (ATLAS_MAG_MIN_FILTER & 0x7)
#define TESTVAR_2 (ATLAS_MAG_MIN_FILTER & 7)

#if (TESTVAR_1 == 0)
    void testFunc() {

    }
#endif
#if (TESTVAR_2 == 0)
    void testFunc2() {

    }
#endif

Error occurred only on line #if (TESTVAR_1 == 0) means TESTVAR_1 is empty.

I'm really surprised there is no error in first define itself...

来源：https://stackoverflow.com/questions/26244930/glsl-if-directive-with

标签

opengl

glsl