[Python-Dev] gcc 4.2 exposes signed integer overflows (original) (raw)

Tim Peters tim.peters at gmail.com
Sun Aug 27 02:37:46 CEST 2006

[David Hopwood]

CPython should be fixed anyway. The correct fix is "if (y == -1 && x < 0 && (unsigned long)x == -(unsigned long)x)".

Note that this was already suggested in the bug report.

[Thomas Wouters]

Why not just "... && x == LONGMIN"?

In full,

if (y == -1 && x == LONG_MIN)

"should work" too. In practice we try to avoid numeric symbols from platform header files because so many platforms have screwed these up over the centuries (search for LONG_BIT or HUGE_VAL ;-)), and because it's better (when possible) not to tie the code to that x was specifically declared as type "long" (e.g., just more stuff that will break if Python decides to make its short int of type PY_LONG_LONG instead). In this specific case, there may also have been a desire to avoid generating a memory load for a fat constant. However, since this is integer division, in real life (outside the test suite) we'll never go beyond the "y == -1" test.

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