[PATCH] D19014: [clang-tidy] Add new checker for suspicious sizeof expressions

[Etienne Bergeron via cfe-commits]

etienneb created this revision.
etienneb added a reviewer: alexfh.
etienneb added a subscriber: cfe-commits.

This check found suspicious cases of sizeof expression.

Sizeof expression is retuning the size (in bytes) of a type or an
expression. Programmers often abuse of misuse this expression.

This checker is adding common set of patterns to detect some
of these bad constructs.


Some examples found by this checker:

R/packages/ifultools/ifultools/src/fra_neig.c
```
        /* free buffer memory */
        (void) mutil_free( dist_buff, sizeof( ctr * sizeof( double ) ) );
        (void) mutil_free( nidx_buff, sizeof( ctr * sizeof( sint32 ) ) );
```


graphviz/v2_20_2/lib/common/utils.c
```
static Dtdisc_t mapDisc = {
    offsetof(item, p),
    sizeof(2 * sizeof(void *)),
    offsetof(item, link),
    (Dtmake_f) newItem,
    (Dtfree_f) freeItem,
    (Dtcompar_f) cmpItem,
    NIL(Dthash_f),
    NIL(Dtmemory_f),
    NIL(Dtevent_f)
};
```


mDNSResponder/mDNSShared/dnsextd.c
```
	context = ( TCPContext* ) malloc( sizeof( TCPContext ) );
	require_action( context, exit, err = mStatus_NoMemoryErr; LogErr( "AcceptTCPConnection", "malloc" ) );
	mDNSPlatformMemZero( context, sizeof( sizeof( TCPContext ) ) );
	context->d		 = self;
```

http://reviews.llvm.org/D19014

Files:
  clang-tidy/misc/CMakeLists.txt
  clang-tidy/misc/MiscTidyModule.cpp
  clang-tidy/misc/SizeofExpressionCheck.cpp
  clang-tidy/misc/SizeofExpressionCheck.h
  docs/clang-tidy/checks/list.rst
  docs/clang-tidy/checks/misc-sizeof-expression.rst
  test/clang-tidy/misc-sizeof-expression.cpp

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