error: Track locations on command line

New LOC_CMDLINE.  Use it for tracking option with argument in
lookup_opt().  We now report errors like this

    qemu: -device smbus-eeprom: Did not find I2C bus for smbus-eeprom

qemu-error.c

@@ -113,6 +113,16 @@ void loc_set_none(void)
     cur_loc->kind = LOC_NONE;
 }
 
+/*
+ * Change the current location to argument ARGV[IDX..IDX+CNT-1].
+ */
+void loc_set_cmdline(char **argv, int idx, int cnt)
+{
+    cur_loc->kind = LOC_CMDLINE;
+    cur_loc->num = cnt;
+    cur_loc->ptr = argv + idx;
+}
+
 /*
  * Change the current location to file FNAME, line LNO.
  */
@@ -143,12 +153,22 @@ void error_set_progname(const char *argv0)
 void error_print_loc(void)
 {
     const char *sep = "";
+    int i;
+    const char *const *argp;
 
     if (!cur_mon) {
         fprintf(stderr, "%s:", progname);
         sep = " ";
     }
     switch (cur_loc->kind) {
+    case LOC_CMDLINE:
+        argp = cur_loc->ptr;
+        for (i = 0; i < cur_loc->num; i++) {
+            error_printf("%s%s", sep, argp[i]);
+            sep = " ";
+        }
+        error_printf(": ");
+        break;
     case LOC_FILE:
         error_printf("%s:", (const char *)cur_loc->ptr);
         if (cur_loc->num) {

qemu-error.h

@@ -15,7 +15,7 @@
 
 typedef struct Location {
     /* all members are private to qemu-error.c */
-    enum { LOC_NONE, LOC_FILE } kind;
+    enum { LOC_NONE, LOC_CMDLINE, LOC_FILE } kind;
     int num;
     const void *ptr;
     struct Location *prev;
@@ -27,6 +27,7 @@ Location *loc_pop(Location *loc);
 Location *loc_save(Location *loc);
 void loc_restore(Location *loc);
 void loc_set_none(void);
+void loc_set_cmdline(char **argv, int idx, int cnt);
 void loc_set_file(const char *fname, int lno);
 
 void error_vprintf(const char *fmt, va_list ap);

vl.c

@@ -4796,6 +4796,7 @@ static const QEMUOption *lookup_opt(int argc, char **argv,
     char *r = argv[optind];
     const char *optarg;
 
+    loc_set_cmdline(argv, optind, 1);
     optind++;
     /* Treat --foo the same as -foo.  */
     if (r[1] == '-')
@@ -4803,8 +4804,7 @@ static const QEMUOption *lookup_opt(int argc, char **argv,
     popt = qemu_options;
     for(;;) {
         if (!popt->name) {
-            fprintf(stderr, "%s: invalid option -- '%s'\n",
-                    argv[0], r);
+            error_report("invalid option");
             exit(1);
         }
         if (!strcmp(popt->name, r + 1))
@@ -4813,11 +4813,11 @@ static const QEMUOption *lookup_opt(int argc, char **argv,
     }
     if (popt->flags & HAS_ARG) {
         if (optind >= argc) {
-            fprintf(stderr, "%s: option '%s' requires an argument\n",
-                    argv[0], r);
+            error_report("requires an argument");
             exit(1);
         }
         optarg = argv[optind++];
+        loc_set_cmdline(argv, optind - 2, 2);
     } else {
         optarg = NULL;
     }
@@ -5662,6 +5662,7 @@ int main(int argc, char **argv, char **envp)
             }
         }
     }
+    loc_set_none();
 
     /* If no data_dir is specified then try to find it relative to the
        executable path.  */