[PATCH 2/2] perf tools: Fix python extension build for gcc 8

[Jiri Olsa]

From: root <root@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>

The gcc 8 won't compile python extension code with
following errors (one example):

  python.c:830:15: error: cast between incompatible  function types from              \
  âPyObject * (*)(struct pyrf_evsel *, PyObject *, PyObject *)â                       \
  uct _object * (*)(struct pyrf_evsel *, struct _object *, struct _object *)â} to     \
  âPyObject * (*)(PyObject *, PyObject *)â {aka âstruct _object * (*)(struct _objeuct \
  _object *)â} [-Werror=cast-function-type]
     .ml_meth  = (PyCFunction)pyrf_evsel__open,

The problem with PyMethodDef::ml_meth callback is that
its type is determined based on PyMethodDef::ml_flags
value, which we set as METH_VARARGS | METH_KEYWORDS.

That indicates that the callback is expecting extra PyObject* arg,
and is actually PyCFunctionWithKeywords type, but the base
PyMethodDef::ml_meth type stays PyCFunction.

Previous gccs did not find this, gcc8 now does. Fixing
this by silencing this warning for python.c build.

Link: http://lkml.kernel.org/n/tip-gyl1jq6b27e9ad0wm9x4v1vr@xxxxxxxxxxxxxx
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 tools/perf/util/setup.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/setup.py b/tools/perf/util/setup.py
index 6891635b50c3..1a3fac37112d 100644
--- a/tools/perf/util/setup.py
+++ b/tools/perf/util/setup.py
@@ -27,7 +27,7 @@ class install_lib(_install_lib):
 
 cflags = getenv('CFLAGS', '').split()
 # switch off several checks (need to be at the end of cflags list)
-cflags += ['-fno-strict-aliasing', '-Wno-write-strings', '-Wno-unused-parameter' ]
+cflags += ['-fno-strict-aliasing', '-Wno-write-strings', '-Wno-unused-parameter', '-Wno-cast-function-type' ]
 
 src_perf  = getenv('srctree') + '/tools/perf'
 build_lib = getenv('PYTHON_EXTBUILD_LIB')
-- 
2.13.6