-Wwrite-strings: Add a PyArg_ParseTupleAndKeywords "const char *" overload

-Wwrite-strings flags code like:

   static char *keywords[] = {"command", "from_tty", "to_string", NULL };

as needing "(char *)" casts, because string literals are "const char []".

We can get rid of the casts by changing the array type like this:

 -  static char *keywords[] = {"command", "from_tty", "to_string", NULL };
 +  static const char *keywords[] = {"command", "from_tty", "to_string", NULL };

However, passing the such array to PyArg_ParseTupleAndKeywords no longer
works OOTB, because PyArg_ParseTupleAndKeywords expects a "char **":

  PyArg_ParseTupleAndKeywords(PyObject *args, PyObject *kw,
                              const char *format,
			      char *keywords[], ...);

and "const char **" is not implicitly convertible to "char **".  C++
is more tolerant that C here WRT aliasing, and a const_cast<char **>
is fine.  However, to avoid having all callers do the cast themselves,
this commit defines a gdb_PyArg_ParseTupleAndKeywords function here
with a corresponding 'keywords' parameter type that does the cast in a
single place.

gdb/ChangeLog:
2017-04-05  Pedro Alves  <palves@redhat.com>

	* python/python-internal.h (gdb_PyArg_ParseTupleAndKeywords): New
	static inline function.
	* python/py-arch.c (archpy_disassemble): Constify 'keywords'
	array and use gdb_PyArg_ParseTupleAndKeywords.
	* python/py-cmd.c (cmdpy_init): Likewise.
	* python/py-finishbreakpoint.c (bpfinishpy_init): Likewise.
	* python/py-inferior.c (infpy_read_memory, infpy_write_memory)
	(infpy_search_memory): Likewise.
	* python/py-objfile.c (objfpy_add_separate_debug_file)
	(gdbpy_lookup_objfile): Likewise.
	* python/py-symbol.c (gdbpy_lookup_symbol)
	(gdbpy_lookup_global_symbol): Likewise.
	* python/py-type.c (gdbpy_lookup_type): Likewise.
	* python/py-value.c (valpy_lazy_string, valpy_string): Likewise.
	* python/python.c (execute_gdb_command, gdbpy_write, gdbpy_flush):
	Likewise.

1 files changed, 5 insertions, 5 deletions

diff --git a/gdb/python/py-objfile.c b/gdb/python/py-objfile.c
index 6a47c17..52f2e1f 100644
--- a/gdb/python/py-objfile.c
+++ b/gdb/python/py-objfile.c
@@ -432,13 +432,13 @@ objfpy_is_valid (PyObject *self, PyObject *args)
 static PyObject *
 objfpy_add_separate_debug_file (PyObject *self, PyObject *args, PyObject *kw)
 {
-  static char *keywords[] = { "file_name", NULL };
+  static const char *keywords[] = { "file_name", NULL };
   objfile_object *obj = (objfile_object *) self;
   const char *file_name;
 
   OBJFPY_REQUIRE_VALID (obj);
 
-  if (!PyArg_ParseTupleAndKeywords (args, kw, "s", keywords, &file_name))
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "s", keywords, &file_name))
     return NULL;
 
   TRY
@@ -559,14 +559,14 @@ objfpy_lookup_objfile_by_build_id (const char *build_id)
 PyObject *
 gdbpy_lookup_objfile (PyObject *self, PyObject *args, PyObject *kw)
 {
-  static char *keywords[] = { "name", "by_build_id", NULL };
+  static const char *keywords[] = { "name", "by_build_id", NULL };
   const char *name;
   PyObject *by_build_id_obj = NULL;
   int by_build_id;
   struct objfile *objfile;
 
-  if (! PyArg_ParseTupleAndKeywords (args, kw, "s|O!", keywords,
-				     &name, &PyBool_Type, &by_build_id_obj))
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "s|O!", keywords,
+					&name, &PyBool_Type, &by_build_id_obj))
     return NULL;
 
   by_build_id = 0;