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Be more careful with type of left operand of <<

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On a 32-bit system, evaluating 1<<31 causes undefined behaviour because
1 is signed and so it produces signed overflow.  UBSan has spotted a
couple of occasions where this happens in Puzzles, so in each case I've
converted the left operand to the unsigned result type we actually want.
This commit is contained in:
Ben Harris
2023-02-26 14:24:38 +00:00
parent 9dbcfa765b
commit 93be3f7cca
2 changed files with 4 additions and 4 deletions
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4
cube.c
View File

@ -202,8 +202,8 @@ struct game_grid {
}; };
#define SET_SQUARE(state, i, val) \ #define SET_SQUARE(state, i, val) \
((state)->bluemask[(i)/32] &= ~(1 << ((i)%32)), \ ((state)->bluemask[(i)/32] &= ~(1UL << ((i)%32)), \
(state)->bluemask[(i)/32] |= ((!!val) << ((i)%32))) (state)->bluemask[(i)/32] |= ((unsigned long)(!!val) << ((i)%32)))
#define GET_SQUARE(state, i) \ #define GET_SQUARE(state, i) \
(((state)->bluemask[(i)/32] >> ((i)%32)) & 1) (((state)->bluemask[(i)/32] >> ((i)%32)) & 1)

4
random.c
View File

@ -254,12 +254,12 @@ unsigned long random_bits(random_state *state, int bits)
} }
/* /*
* `(1 << bits) - 1' is not good enough, since if bits==32 on a * `(1UL << bits) - 1' is not good enough, since if bits==32 on a
* 32-bit machine, behaviour is undefined and Intel has a nasty * 32-bit machine, behaviour is undefined and Intel has a nasty
* habit of shifting left by zero instead. We'll shift by * habit of shifting left by zero instead. We'll shift by
* bits-1 and then separately shift by one. * bits-1 and then separately shift by one.
*/ */
ret &= (1 << (bits-1)) * 2 - 1; ret &= (1UL << (bits-1)) * 2 - 1;
return ret; return ret;
} }