[RFC/PATCH] Makefile: add cppcheck target

[Chris Packham <judge.packham@gmail.com>]

Add cppcheck target to Makefile. Cppcheck is a static
analysis tool for C/C++ code. Cppcheck primarily detects
the types of bugs that the compilers normally do not detect.
It is an useful target for doing QA analysis.

Based-on-patch-by: Elia Pinto <gitter.spiros@gmail.com>
Signed-off-by: Chris Packham <judge.packham@gmail.com>
---
I had been playing with cppcheck for some other projects and happened to
notice [1] in the archives. This is my attempt to resolve the feedback
that Junio made at the time.

In terms of errors that are actually reported there are only a few

$ make cppcheck
cppcheck --force --quiet --inline-suppr  .
[compat/nedmalloc/malloc.c.h:4093]: (error) Possible null pointer dereference: sp
[compat/nedmalloc/malloc.c.h:4106]: (error) Possible null pointer dereference: sp
[compat/nedmalloc/nedmalloc.c:551]: (error) Expression '*(&p.mycache)=TlsAlloc(),TLS_OUT_OF_INDEXES==*(&p.mycache)' depends on order of evaluation of side effects
[compat/regex/regcomp.c:3086]: (error) Memory leak: sbcset
[compat/regex/regcomp.c:3634]: (error) Memory leak: sbcset
[compat/regex/regcomp.c:3086]: (error) Memory leak: mbcset
[compat/regex/regcomp.c:3634]: (error) Memory leak: mbcset
[compat/regex/regcomp.c:2802]: (error) Uninitialized variable: table_size
[compat/regex/regcomp.c:2805]: (error) Uninitialized variable: table_size
[compat/regex/regcomp.c:532]: (error) Memory leak: fastmap
[t/t4051/appended1.c:3]: (error) Invalid number of character '{' when these macros are defined: ''.
[t/t4051/appended2.c:35]: (error) Invalid number of character '{' when these macros are defined: ''.

The last 2 are just false positives from test data. I haven't looked
into any of the others.

I've also provisioned for enabling extra checks by passing CPPCHECK_ADD
in the make invocation.

$ make cppcheck CPPCHECK_ADD=--enable=all
... lots of output
    
[1] - http://public-inbox.org/git/1390993371-2431-1-git-send-email-gitter.spiros@gmail.com/#t

 Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Makefile b/Makefile
index f53fcc90d..8b5976d88 100644
--- a/Makefile
+++ b/Makefile
@@ -2635,3 +2635,7 @@ cover_db: coverage-report
 cover_db_html: cover_db
 	cover -report html -outputdir cover_db_html cover_db
 
+.PHONY: cppcheck
+
+cppcheck:
+	cppcheck --force --quiet --inline-suppr $(CPPCHECK_ADD) .
-- 
2.11.0.24.ge6920cf