[clang-tidy] Add checker for operations between integrals and pointers

Summary:
This check is finding suspicious operations involving pointers and integral types; which are most likely bugs.

Examples:
subversion/v1_6/subversion/libsvn_subr/utf.c
```
static const char *
fuzzy_escape(const char *src, apr_size_t len, apr_pool_t *pool)
{
  [...]
   while (src_orig < src_end)
    {
      if (! svn_ctype_isascii(*src_orig) || src_orig == '\0')   // Should be *src_orig
        {
```

apache2/v2_2_23/modules/metadata/mod_headers.c
```
static char *parse_format_tag(apr_pool_t *p, format_tag *tag, const char **sa)
{
  [...]
    tag->arg = '\0';   // ERROR: tag->arg has type char*

    /* grab the argument if there is one */
    if (*s == '{') {
        ++s;
        tag->arg = ap_getword(p,&s,'}');
    }
```

Reviewers: alexfh

Subscribers: Eugene.Zelenko, cfe-commits

Differential Revision: http://reviews.llvm.org/D19118

llvm-svn: 266450

1 files changed, 30 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/misc-pointer-and-integral-operation.cpp b/clang-tools-extra/test/clang-tidy/misc-pointer-and-integral-operation.cpp
new file mode 100644
index 00000000000..6591f0af360
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/misc-pointer-and-integral-operation.cpp
@@ -0,0 +1,30 @@
+// RUN: %check_clang_tidy %s misc-pointer-and-integral-operation %t
+
+bool* pb;
+char* pc;
+int* pi;
+
+int Test() {
+  if (pi < 0) return 0;
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: suspicious comparison of pointer with zero [misc-pointer-and-integral-operation]
+  if (pi <= 0) return 0;
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: suspicious comparison of pointer with zero
+
+  if (nullptr <= pb) return 0;
+  // CHECK-MESSAGES: :[[@LINE-1]]:15: warning: suspicious comparison of pointer with null
+  if (pc < nullptr) return 0;
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: suspicious comparison of pointer with null
+  if (pi > nullptr) return 0;
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: suspicious comparison of pointer with null
+
+  return 1;
+}
+
+int Valid() {
+  *pb = false;
+  *pc = '\0';
+
+  pi += (pi != nullptr);
+  pi -= (pi == nullptr);
+  pc += (pb != nullptr);
+}