[LLVMbugs] [Bug 10795] New: Extend memset-like sizeof() checks to *alloc

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sat Aug 27 16:08:52 PDT 2011


           Summary: Extend memset-like sizeof() checks to *alloc
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: joerg at NetBSD.org
                CC: llvmbugs at cs.uiuc.edu

It would be nice if malloc and friends had type-based diagnostic like memset:

foo = malloc(sizeof(bar))

should check whether:

(1) typeof(foo) == typeof(bar) --> warning

(2) sizeof(bar) < sizeof(foo) --> warning

foo = (bar *)malloc(...)

should additionally check that typeof(foo) == bar * and recomment removing the
cast. This is pre-ANSI style.

A static analyzer for expressions of the form malloc(x * sizeof(y)) etc might
be useful if x can't be proven to be small enough to not trigger overflow.

A static analyzer check for the following idiom would be nice:

foo = malloc(len);
memset(foo, 0, len);

--> foo = calloc(1, len);

foo = malloc(x * sizeof(**foo));
memset(foo, 0, x * sizeof(**foo));

--> foo = calloc(x, sizeof(**foo));

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