I have a Fragment shader that contains:

float c = texture2D(tex, tc).a;
float alpha = mix(0.0f, 1.0f, c);
gl_FragColor = vec4(1, 1, 1, alpha) * color;

This works fine on my desktop and Nexus 5. However I get an exception while running on a Wiko mobile:

0:22: L0001: Expected token ')', found 'identifier'

Line 22 is the line containing the mix function.

What I'm doing wrong?

  • 2
    \$\begingroup\$ You seem to be missing a semicolon at the end of the line float c = texture2D... — is that present in the original? It could be that some platforms' shader compilers fix this common error automatically, but the one that's throwing the exception doesn't. \$\endgroup\$
    – DMGregory
    Mar 29, 2017 at 13:32
  • \$\begingroup\$ Thanks DMGregory, it was just a mistake when I pasted the code \$\endgroup\$
    – FloFu
    Mar 29, 2017 at 13:59
  • \$\begingroup\$ Just by the way, do you have #version directive in the shader? \$\endgroup\$ Mar 29, 2017 at 14:37
  • \$\begingroup\$ HolyBlackCat, I have a #version 100 directive \$\endgroup\$
    – FloFu
    Mar 29, 2017 at 15:02

1 Answer 1


Depending on your driver and GLSL version, the "f" suffix on floats may be illegal. Change to:

float alpha = mix(0.0, 1.0, c);

As always, OS is irrelevant; you really need to say what hardware (in particular what GPU) you have.

  • \$\begingroup\$ Thanks, this was the issue. Next time I'll remember about the hardware and GPU :) \$\endgroup\$
    – FloFu
    Mar 29, 2017 at 14:00
  • \$\begingroup\$ Sometimes OS matters, even within a single vendor's drivers. I've had Catalyst shader bugs that only manifested on one OS or another. \$\endgroup\$ Mar 30, 2017 at 1:05
  • \$\begingroup\$ @LarsViklund - that's not the OS, it's the driver. The driver is OS-specific for sure, but it's still the driver. \$\endgroup\$ Mar 30, 2017 at 6:58
  • \$\begingroup\$ @LeComteduMerde-fou I did deploy what was claimed to be identical drivers on Windows and Linux, upstream couldn't repro on Windows. Sometimes variations happen. \$\endgroup\$ Apr 1, 2017 at 17:32

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