[PATCH] D14203: [analyzer] Improve pointer arithmetic checker.

Gábor Horváth via cfe-commits cfe-commits at lists.llvm.org
Fri Oct 30 08:38:12 PDT 2015

xazax.hun created this revision.
xazax.hun added reviewers: zaks.anna, dcoughlin.
xazax.hun added subscribers: cfe-commits, dkrupp.

This patch is intended to improve pointer arithmetic checker.

>From now on it tries to only warn, when the pointer arithmetic is likely to cause an error. For example when the pointer points to a single object, or an array of derived types.

Note that this check does not free the stored information right now, because it caused some trouble when I was checking the following code.

struct trie {
  struct trie* next;

struct kwset {
  struct trie *trie;
  unsigned char y[10];
  struct trie* next[10];
  int d;

typedef struct trie trie_t;
typedef struct kwset kwset_t;

void f(kwset_t *kws, char const *p, char const *q) {
  struct trie const *trie;
  struct trie * const *next = kws->next;
  register unsigned char c;
  register char const *end = p;
  register char const *lim = q;
  register int d = 1;
  register unsigned char const *y = kws->y;

  d = y[c = (end+=d)[-1]];
  trie = next[c]; // Here the analyzer tought that kws->next is a dead region, so the stored information was unavailable for the array. adding a kws = 0 or similar line to the end of the function fixed the problem. Is this a bug in liveness analysis fo regions?



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