On 11/20/2014 05:33 AM, Neil Roberts wrote: > For what it's worth, I did a quick grep through the internal and public > shader-db and I couldn't find anything using this. > > git grep -P '\b(?<!e[+-])(?<![.0-9])[0-9]+f\b' > > If AMD disallows it then it seems like it would be reasonably safe to > disallow it in Mesa too. > > GCC disallows it too which could be an indication that people won't have > a habit of using it.
So... the GLSL spec actually follows C? Then we should definitely follow the spec, and there's no need for a GLSL spec bug. If AMD disallows it, then there are not likely to be any applications that depend on it... so I agree with Neil that we're safe to disallow it too. I'm still curious about glslang... if glslang allows it, I'll file a bug against glslang. :) > - Neil > > Iago Toral <ito...@igalia.com> writes: > >> On Thu, 2014-11-20 at 08:08 +0100, Iago Toral wrote: >>> On Wed, 2014-11-19 at 10:27 -0800, Ian Romanick wrote: >>>> On 11/19/2014 03:47 AM, Iago Toral Quiroga wrote: >>>>> Hi, >>>>> >>>>> I came across a GLSL test that checks that doing something like this in >>>>> a shader should fail: >>>> >>>> Is this one of the dEQP tests? >>> >>> Yes. >>> >>>>> float value = 1f; >>>> >>>> It seems like we have a test related to this in piglit somewhere... it >>>> looks like tests/shaders/glsl-floating-constant-120.shader_test uses >>>> that syntax, but it's not explicitly testing that feature. >>>> >>>>> However, this works fine in Mesa. Checking the spec I see: >>>>> >>>>> Floating-point constants are defined as follows. >>>>> floating-constant: >>>>> fractional-constant exponent-part(opt) floating-suffix(opt) >>>>> digit-sequence exponent-part floating-suffix(opt) >>>>> fractional-constant: >>>>> digit-sequence . digit-sequence >>>>> digit-sequence . >>>>> . digit-sequence >>>>> exponent-part: >>>>> e sign(opt) digit-sequence >>>>> E sign(opt) digit-sequence >>>>> sign: one of >>>>> + - >>>>> digit-sequence: >>>>> digit >>>>> digit-sequence digit >>>>> floating-suffix: one of >>>>> f F >>>>> >>>>> which suggests that the test is correct and Mesa has a bug. According to >>>>> the above rules, however, something like this is fine: >>>>> >>>>> float f = 1e2f; >>>>> >>>>> which I find kind of weird if the other case is not valid, so I wonder >>>>> if there is a bug in the spec or this is on purpose for some reason that >>>>> I am missing. >>>>> >>>>> Then, to make matters worse, I read this in opengl.org wiki [1]: >>>>> >>>>> "A numeric literal that uses a decimal is by default of type float. To >>>>> create a float literal from an integer value, use the suffix f or F as >>>>> in C/C++." >>>>> >>>>> which contradicts the spec and the test and is aligned with the current >>>>> way Mesa works. >>>>> >>>>> So: does anyone know what version is right? Could this be a bug in the >>>>> spec? and if it is not, do we want to change the behavior to follow the >>>>> spec as it is now? >>>> >>>> The $64,000 question: What do other GLSL compilers (including, perhaps, >>>> glslang) do? This seems like one of the cases where nobody is likely to >>>> follow the spec, and some application will depend on that. If that's >>>> the case, I'll submit a spec bug. >>> >>> Good point. I'll try to check a few cases and reply here. Thanks! >> >> I did a quick test on AMD Radeon and nVidia proprietary drivers since I >> had these easily available. AMD fails to compile (so it follows the >> spec) but nVidia works (so same case as Mesa). >> >> This confirms your guess: different drivers are doing different things. >> Is this enough to file a spec bug? I imagine that the result on glslang >> won't change anything, but I can try to install it and test there too if >> you think that's interesting anyway. >> >> Iago >> >> _______________________________________________ >> mesa-dev mailing list >> mesa-dev@lists.freedesktop.org >> http://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev