glTexImage* functions state that floating point values are always clamped.

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Consider the statement for a format of GL_RED:

Each element is a single red component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for green and blue, and 1 for alpha. Each component is clamped to the range [0,1].

This is incorrect. Clamping should only happen for normalized integer internal formats. The ES 3.0 documentation is more correct in this regard.