Support 'help' as a synonym for '?' in command line options

For command line options which permit '?' meaning 'please list the
permitted values', add support for 'help' as a synonym, by abstracting
the check out into a helper function.

This change means that in some cases where we were being lazy in
our string parsing, "?junk" will now be rejected as an invalid option
rather than being (undocumentedly) treated the same way as "?".

Update the documentation to use 'help' rather than '?', since '?'
is a shell metacharacter and thus prone to fail confusingly if there
is a single character filename in the current working directory and
the '?' has not been escaped. It's therefore better to steer users
towards 'help', though '?' is retained for backwards compatibility.

We do not, however, update the output of the system emulator's -help
(or any documentation autogenerated from the qemu-options.hx which
is the source of the -help text) because libvirt parses our -help
output and will break. At a later date when QEMU provides a better
interface so libvirt can avoid having to do this, we can update the
-help text too.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

3 files changed, 4 insertions, 4 deletions

diff --git a/hw/mips_jazz.c b/hw/mips_jazz.c
index bf1b799c4d..db927f14d0 100644
--- a/hw/mips_jazz.c
+++ b/hw/mips_jazz.c
@@ -239,7 +239,7 @@ static void mips_jazz_init(MemoryRegion *address_space,
             dp83932_init(nd, 0x80001000, 2, get_system_memory(), rc4030[4],
                          rc4030_opaque, rc4030_dma_memory_rw);
             break;
-        } else if (strcmp(nd->model, "?") == 0) {
+        } else if (is_help_option(nd->model)) {
             fprintf(stderr, "qemu: Supported NICs: dp83932\n");
             exit(1);
         } else {
diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c
index 7915b4500d..b22a37a00c 100644
--- a/hw/qdev-monitor.c
+++ b/hw/qdev-monitor.c
@@ -138,13 +138,13 @@ int qdev_device_help(QemuOpts *opts)
     ObjectClass *klass;
 
     driver = qemu_opt_get(opts, "driver");
-    if (driver && !strcmp(driver, "?")) {
+    if (driver && is_help_option(driver)) {
         bool show_no_user = false;
         object_class_foreach(qdev_print_devinfo, TYPE_DEVICE, false, &show_no_user);
         return 1;
     }
 
-    if (!driver || !qemu_opt_get(opts, "?")) {
+    if (!driver || !qemu_opt_has_help_opt(opts)) {
         return 0;
     }
 
diff --git a/hw/watchdog.c b/hw/watchdog.c
index a42124d520..b52acedd98 100644
--- a/hw/watchdog.c
+++ b/hw/watchdog.c
@@ -55,7 +55,7 @@ int select_watchdog(const char *p)
     QemuOpts *opts;
 
     /* -watchdog ? lists available devices and exits cleanly. */
-    if (strcmp(p, "?") == 0) {
+    if (is_help_option(p)) {
         QLIST_FOREACH(model, &watchdog_list, entry) {
             fprintf(stderr, "\t%s\t%s\n",
                      model->wdt_name, model->wdt_description);