[analyzer] Discard malloc-overflow bug-report when a known size is malloc'ed.

This patch ignores malloc-overflow bug in two cases:
Case1:
x = a/b; where n < b
malloc (x*n); Then x*n will not overflow.

Case2:
x = a; // when 'a' is a known value.
malloc (x*n);

Also replaced isa with dyn_cast.

Reject multiplication by zero cases in MallocOverflowSecurityChecker
Currently MallocOverflowSecurityChecker does not catch cases like:
malloc(n * 0 * sizeof(int));

This patch rejects such cases.

Two test cases added. malloc-overflow2.c has an example inspired from a code
in linux kernel where the current checker flags a warning while it should not.

A patch by Aditya Kumar!

Differential Revision: http://reviews.llvm.org/D9924

llvm-svn: 248446

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/test/Analysis/malloc-overflow.c b/clang/test/Analysis/malloc-overflow.c
index 2f443caf4a1..99e05adab6f 100644
--- a/clang/test/Analysis/malloc-overflow.c
+++ b/clang/test/Analysis/malloc-overflow.c
@@ -102,7 +102,7 @@ void * f13(struct s13 *s)
 {
   if (s->n > 10)
     return NULL;
-  return malloc(s->n * sizeof(int));  // no warning
+  return malloc(s->n * sizeof(int)); // no-warning
 }
 
 void * f14(int n)