[Qemu-devel] [PATCH v3 1/6] qemu-option: Allow integer defaults

[Eric Blake <eblake@redhat.com>]

Set the framework up for declaring integer options with an integer
default, instead of our current insane approach of requiring the
default value to be given as a string (which then has to be reparsed
at every use that wants a number).  git grep '[^.]def_value_str' says
that we have done a good job of NOT abusing the internal field
outside of the implementation in qemu-option.c; therefore, it is not
too hard to audit that all code can either handle the new integer
defaults correctly or abort because a caller violated constraints.
Sadly, we DO have a constraint that qemu_opt_get() should not be
called on an option that has an integer type, because we have no
where to stash a cached const char * result; but callers that want
an integer should be using qemu_opt_get_number() and friends
anyways.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/qemu/option.h | 12 ++++++++
 util/qemu-option.c    | 69 +++++++++++++++++++++++++++++++++++++------
 2 files changed, 72 insertions(+), 9 deletions(-)

diff --git a/include/qemu/option.h b/include/qemu/option.h
index 844587cab39..46b80d5a6e1 100644
--- a/include/qemu/option.h
+++ b/include/qemu/option.h
@@ -46,6 +46,18 @@ typedef struct QemuOptDesc {
     const char *name;
     enum QemuOptType type;
     const char *help;
+    /*
+     * For QEMU_OPT_STRING: Leave def_value_int 0, and set def_value_str
+     * to a default value or leave NULL for no default.
+     *
+     * For other types: Initialize at most non-zero def_value_int or a
+     * parseable def_value_str for a default (must use a string for an
+     * explicit default of 0, although an implicit default generally
+     * works).  If setting def_value_int, calling qemu_opt_get() on
+     * that option will abort(); instead, call qemu_opt_get_del() or a
+     * typed getter.
+     */
+    uint64_t def_value_int;
     const char *def_value_str;
 } QemuOptDesc;

diff --git a/util/qemu-option.c b/util/qemu-option.c
index de42e2a406a..06c4e8102a8 100644
--- a/util/qemu-option.c
+++ b/util/qemu-option.c
@@ -321,7 +321,8 @@ const char *qemu_opt_get(QemuOpts *opts, const char *name)
     opt = qemu_opt_find(opts, name);
     if (!opt) {
         const QemuOptDesc *desc = find_desc_by_name(opts->list->desc, name);
-        if (desc && desc->def_value_str) {
+        if (desc) {
+            assert(!desc->def_value_int);
             return desc->def_value_str;
         }
     }
@@ -364,8 +365,22 @@ char *qemu_opt_get_del(QemuOpts *opts, const char *name)
     opt = qemu_opt_find(opts, name);
     if (!opt) {
         desc = find_desc_by_name(opts->list->desc, name);
-        if (desc && desc->def_value_str) {
-            str = g_strdup(desc->def_value_str);
+        if (desc) {
+            if (desc->def_value_str) {
+                str = g_strdup(desc->def_value_str);
+            } else if (desc->def_value_int) {
+                switch (desc->type) {
+                case QEMU_OPT_BOOL:
+                    str = g_strdup("on");
+                    break;
+                case QEMU_OPT_NUMBER:
+                case QEMU_OPT_SIZE:
+                    str = g_strdup_printf("%" PRId64, desc->def_value_int);
+                    break;
+                default:
+                    abort();
+                }
+            }
         }
         return str;
     }
@@ -400,8 +415,15 @@ static bool qemu_opt_get_bool_helper(QemuOpts *opts, const char *name,
     opt = qemu_opt_find(opts, name);
     if (opt == NULL) {
         const QemuOptDesc *desc = find_desc_by_name(opts->list->desc, name);
-        if (desc && desc->def_value_str) {
-            parse_option_bool(name, desc->def_value_str, &ret, &error_abort);
+        if (desc) {
+            if (desc->def_value_int) {
+                assert(desc->type != QEMU_OPT_STRING);
+                return true;
+            }
+            if (desc->def_value_str) {
+                parse_option_bool(name, desc->def_value_str, &ret,
+                                  &error_abort);
+            }
         }
         return ret;
     }
@@ -436,8 +458,15 @@ static uint64_t qemu_opt_get_number_helper(QemuOpts *opts, const char *name,
     opt = qemu_opt_find(opts, name);
     if (opt == NULL) {
         const QemuOptDesc *desc = find_desc_by_name(opts->list->desc, name);
-        if (desc && desc->def_value_str) {
-            parse_option_number(name, desc->def_value_str, &ret, &error_abort);
+        if (desc) {
+            if (desc->def_value_int) {
+                assert(desc->type != QEMU_OPT_STRING);
+                return desc->def_value_int;
+            }
+            if (desc->def_value_str) {
+                parse_option_number(name, desc->def_value_str, &ret,
+                                    &error_abort);
+            }
         }
         return ret;
     }
@@ -473,8 +502,15 @@ static uint64_t qemu_opt_get_size_helper(QemuOpts *opts, const char *name,
     opt = qemu_opt_find(opts, name);
     if (opt == NULL) {
         const QemuOptDesc *desc = find_desc_by_name(opts->list->desc, name);
-        if (desc && desc->def_value_str) {
-            parse_option_size(name, desc->def_value_str, &ret, &error_abort);
+        if (desc) {
+            if (desc->def_value_int) {
+                assert(desc->type != QEMU_OPT_STRING);
+                return desc->def_value_int;
+            }
+            if (desc->def_value_str) {
+                parse_option_size(name, desc->def_value_str, &ret,
+                                  &error_abort);
+            }
         }
         return ret;
     }
@@ -787,9 +823,23 @@ void qemu_opts_print(QemuOpts *opts, const char *separator)
     }
     for (; desc && desc->name; desc++) {
         const char *value;
+        char *tmp = NULL;
         opt = qemu_opt_find(opts, desc->name);

         value = opt ? opt->str : desc->def_value_str;
+        if (!value && desc->def_value_int) {
+            switch (desc->type) {
+            case QEMU_OPT_BOOL:
+                value = tmp = g_strdup("on");
+                break;
+            case QEMU_OPT_NUMBER:
+            case QEMU_OPT_SIZE:
+                value = tmp = g_strdup_printf("%" PRId64, desc->def_value_int);
+                break;
+            default:
+                abort();
+            }
+        }
         if (!value) {
             continue;
         }
@@ -803,6 +853,7 @@ void qemu_opts_print(QemuOpts *opts, const char *separator)
             printf("%s%s=%s", sep, desc->name, value);
         }
         sep = separator;
+        g_free(tmp);
     }
 }

-- 
2.20.1