QColor: Fix UB (left shift of negative number)

If hex2int(const char*) is called with invalid input, it is expected to
return a negative value. However, it didn't check the return value of
h2i() before attempting a left-shift on it, leading to UB when the first
digit was already invalid.

UBSan agrees:

  qcolor_p.cpp:55:23: runtime error: left shift of negative value -1

This is particularly worrisome as the function can be called with
unsanitized input.

Fix by checking each value for non-negativity, returning -1 early
when errors are detected.

Also port to QtMiscUtils::fromHex() and add some docs.

Change-Id: I33dbc157ffb4fbfba27113a0a008eef35c1055f7
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

0 files changed, 0 insertions, 0 deletions