arith: Detect error in bitwise shifting
yash/branches/arith-error/arith.c (diff)| @@ -443,9 +443,18 @@ | ||
| 443 | 443 | { |
| 444 | 444 | switch (ttype) { |
| 445 | 445 | case TT_LESSLESS: case TT_LESSLESSEQUAL: |
| 446 | + if (v1 < 0) | |
| 447 | + goto negative_left_shift; | |
| 448 | + if (v2 < 0 || v2 >= LONG_BIT) | |
| 449 | + goto invalid_shift_width; | |
| 450 | + unsigned long u1 = (unsigned long) v1; | |
| 451 | + if ((u1 << v2 & (unsigned long) LONG_MAX) >> v2 != u1) | |
| 452 | + goto overflow; | |
| 446 | 453 | *result = v1 << v2; |
| 447 | 454 | return true; |
| 448 | 455 | case TT_GREATERGREATER: case TT_GREATERGREATEREQUAL: |
| 456 | + if (v2 < 0 || v2 >= LONG_BIT) | |
| 457 | + goto invalid_shift_width; | |
| 449 | 458 | *result = v1 >> v2; |
| 450 | 459 | return true; |
| 451 | 460 | case TT_AMP: case TT_AMPEQUAL: |
| @@ -460,6 +469,16 @@ | ||
| 460 | 469 | default: |
| 461 | 470 | assert(false); |
| 462 | 471 | } |
| 472 | + | |
| 473 | +overflow: | |
| 474 | + xerror(0, Ngt("arithmetic: overflow")); | |
| 475 | + return false; | |
| 476 | +negative_left_shift: | |
| 477 | + xerror(0, Ngt("arithmetic: negative value cannot be shifted to left")); | |
| 478 | + return false; | |
| 479 | +invalid_shift_width: | |
| 480 | + xerror(0, Ngt("arithmetic: invalid shift width")); | |
| 481 | + return false; | |
| 463 | 482 | } |
| 464 | 483 | |
| 465 | 484 | /* Applies binary operator `ttype' to the given operands `v1' and `v2'. */ |
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