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author | Alexander Monakov <amonakov@ispras.ru> | 2017-09-29 19:00:15 +0300 |
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committer | Alexander Monakov <amonakov@gcc.gnu.org> | 2017-09-29 19:00:15 +0300 |
commit | 9e686ea1c952dd513cf98c2cec464b3533ba763c (patch) | |
tree | 1cfc0484d5e64853823c1322638c2787aa3877ce /gcc/vec.c | |
parent | cd644ae2bc0ce62b88f786ce5a68ad0ba2509ec6 (diff) | |
download | gcc-9e686ea1c952dd513cf98c2cec464b3533ba763c.zip gcc-9e686ea1c952dd513cf98c2cec464b3533ba763c.tar.gz gcc-9e686ea1c952dd513cf98c2cec464b3533ba763c.tar.bz2 |
qsort comparator consistency checking
* genmodes.c (calc_wider_mode): Suppress qsort macro.
* system.h [CHECKING_P] (qsort): Redirect to qsort_chk.
(qsort_chk): Declare.
* vec.c [CHECKING_P] (qsort_chk_error): New static function.
(qsort_chk): New function.
From-SVN: r253295
Diffstat (limited to 'gcc/vec.c')
-rw-r--r-- | gcc/vec.c | 93 |
1 files changed, 93 insertions, 0 deletions
@@ -31,6 +31,12 @@ along with GCC; see the file COPYING3. If not see #include "coretypes.h" #include "hash-table.h" #include "selftest.h" +#ifdef GENERATOR_FILE +#include "errors.h" +#else +#include "input.h" +#include "diagnostic-core.h" +#endif /* vNULL is an empty type with a template cast operation that returns a zero-initialized vec<T, A, L> instance. Use this when you want @@ -190,6 +196,93 @@ dump_vec_loc_statistics (void) vec_mem_desc.dump (VEC_ORIGIN); } +#if CHECKING_P +/* Report qsort comparator CMP consistency check failure with P1, P2, P3 as + witness elements. */ +ATTRIBUTE_NORETURN ATTRIBUTE_COLD +static void +qsort_chk_error (const void *p1, const void *p2, const void *p3, + int (*cmp) (const void *, const void *)) +{ + if (!p3) + { + int r1 = cmp (p1, p2), r2 = cmp (p2, p1); + error ("qsort comparator not anti-commutative: %d, %d", r1, r2); + } + else if (p1 == p2) + { + int r = cmp (p1, p3); + error ("qsort comparator non-negative on sorted output: %d", r); + } + else + { + int r1 = cmp (p1, p2), r2 = cmp (p2, p3), r3 = cmp (p1, p3); + error ("qsort comparator not transitive: %d, %d, %d", r1, r2, r3); + } + internal_error ("qsort checking failed"); +} + +/* Wrapper around qsort with checking that CMP is consistent on given input. + + Strictly speaking, passing invalid (non-transitive, non-anti-commutative) + comparators to libc qsort can result in undefined behavior. Therefore we + should ideally perform consistency checks prior to invoking qsort, but in + order to do that optimally we'd need to sort the array ourselves beforehand + with a sorting routine known to be "safe". Instead, we expect that most + implementations in practice will still produce some permutation of input + array even for invalid comparators, which enables us to perform checks on + the output array. */ +void +qsort_chk (void *base, size_t n, size_t size, + int (*cmp)(const void *, const void *)) +{ + (qsort) (base, n, size, cmp); +#if 0 +#define LIM(n) (n) +#else + /* Limit overall time complexity to O(n log n). */ +#define LIM(n) ((n) <= 16 ? (n) : 12 + floor_log2 (n)) +#endif +#define ELT(i) ((const char *) base + (i) * size) +#define CMP(i, j) cmp (ELT (i), ELT (j)) +#define ERR2(i, j) qsort_chk_error (ELT (i), ELT (j), NULL, cmp) +#define ERR3(i, j, k) qsort_chk_error (ELT (i), ELT (j), ELT (k), cmp) + size_t i1, i2, i, j; + /* This outer loop iterates over maximum spans [i1, i2) such that + elements within each span compare equal to each other. */ + for (i1 = 0; i1 < n; i1 = i2) + { + /* Position i2 one past last element that compares equal to i1'th. */ + for (i2 = i1 + 1; i2 < n; i2++) + if (CMP (i1, i2)) + break; + else if (CMP (i2, i1)) + return ERR2 (i1, i2); + size_t lim1 = LIM (i2 - i1), lim2 = LIM (n - i2); + /* Verify that other pairs within current span compare equal. */ + for (i = i1 + 1; i + 1 < i2; i++) + for (j = i + 1; j < i1 + lim1; j++) + if (CMP (i, j)) + return ERR3 (i, i1, j); + else if (CMP (j, i)) + return ERR2 (i, j); + /* Verify that elements within this span compare less than + elements beyond the span. */ + for (i = i1; i < i2; i++) + for (j = i2; j < i2 + lim2; j++) + if (CMP (i, j) >= 0) + return ERR3 (i, i1, j); + else if (CMP (j, i) <= 0) + return ERR2 (i, j); + } +#undef ERR3 +#undef ERR2 +#undef CMP +#undef ELT +#undef LIM +} +#endif /* #if CHECKING_P */ + #ifndef GENERATOR_FILE #if CHECKING_P |