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UAPI: ndctl: Fix g++-unsupported initialisation in headers
authorDavid Howells <dhowells@redhat.com>
Thu, 6 Sep 2018 09:19:24 +0000 (10:19 +0100)
committerDan Williams <dan.j.williams@intel.com>
Wed, 17 Oct 2018 20:56:54 +0000 (13:56 -0700)
commit9607871f37dc3e717639694b8d0dc738f2a68efc
treea794e8920d636d4ea86e2e9eb31b1b57f6c80167
parentf110176633d74bbac1f80ab9b9c6b83ea3e1cc23
UAPI: ndctl: Fix g++-unsupported initialisation in headers

The following code in the linux/ndctl header file:

static inline const char *nvdimm_bus_cmd_name(unsigned cmd)
{
static const char * const names[] = {
[ND_CMD_ARS_CAP] = "ars_cap",
[ND_CMD_ARS_START] = "ars_start",
[ND_CMD_ARS_STATUS] = "ars_status",
[ND_CMD_CLEAR_ERROR] = "clear_error",
[ND_CMD_CALL] = "cmd_call",
};

if (cmd < ARRAY_SIZE(names) && names[cmd])
return names[cmd];
return "unknown";
}

is broken in a number of ways:

 (1) ARRAY_SIZE() is not generally defined.

 (2) g++ does not support "non-trivial" array initialisers fully yet.

 (3) Every file that calls this function will acquire a copy of names[].

The same goes for nvdimm_cmd_name().

Fix all three by converting to a switch statement where each case returns a
string.  That way if cmd is a constant, the compiler can trivially reduce it
and, if not, the compiler can use a shared lookup table if it thinks that is
more efficient.

A better way would be to remove these functions and their arrays from the
header entirely.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
include/uapi/linux/ndctl.h