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| -rw-r--r-- | src/src/expand.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/src/src/expand.c b/src/src/expand.c index 2e59c4084..d1b81678b 100644 --- a/src/src/expand.c +++ b/src/src/expand.c @@ -3106,6 +3106,32 @@ if (*error == NULL) int op = *s++; int y = eval_op_unary(&s, decimal, error); if (*error != NULL) break; + /* SIGFPE both on div/mod by zero and on INT_MIN / -1, which would give + * a value of INT_MAX+1. Note that INT_MIN * -1 gives INT_MIN for me, which + * is a bug somewhere in [gcc 4.2.1, FreeBSD, amd64]. In fact, -N*-M where + * -N*M is INT_MIN will yielf INT_MIN. + * Since we don't support floating point, this is somewhat simpler. + * Ideally, we'd return an error, but since we overflow for all other + * arithmetic, consistency suggests otherwise, but what's the correct value + * to use? There is none. + * The C standard guarantees overflow for unsigned arithmetic but signed + * overflow invokes undefined behaviour; in practice, this is overflow + * except for converting INT_MIN to INT_MAX+1. We also can't guarantee + * that long/longlong larger than int are available, or we could just work + * with larger types. We should consider whether to guarantee 32bit eval + * and 64-bit working variables, with errors returned. For now ... + * So, the only SIGFPEs occur with a non-shrinking div/mod, thus -1; we + * can just let the other invalid results occur otherwise, as they have + * until now. For this one case, we can coerce. + */ + if (y == -1 && x == INT_MIN && op != '*') + { + DEBUG(D_expand) + debug_printf("Integer exception dodging: %d%c-1 coerced to %d\n", + INT_MIN, op, INT_MAX); + x = INT_MAX; + continue; + } if (op == '*') x *= y; else |