Re: [Qemu-devel] [PATCH] qemu-option: Include name of invalid parameter in error message

[Stefan Weil]

Am 02.08.2010 10:40, schrieb Markus Armbruster:
> Stefan Weil <address@hidden> writes:
>
> > All other error messages in qemu-option.c display the name
> > of the invalid parameter. This seems to be reasonable for
> > invalid identifiers, too. Without it, a debugger is needed
> > to find the name.
> >
> > Cc: Markus Armbruster <address@hidden>
> > Cc: Anthony Liguori <address@hidden>
> > Signed-off-by: Stefan Weil <address@hidden>
> > ---
> > qemu-option.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/qemu-option.c b/qemu-option.c
> > index 1f8f41a..ccea267 100644
> > --- a/qemu-option.c
> > +++ b/qemu-option.c
> > @@ -694,7 +694,7 @@ QemuOpts *qemu_opts_create(QemuOptsList *list, 
> > const char *id, int fail_if_exist
> >
> > if (id) {
> > if (!id_wellformed(id)) {
> > - qerror_report(QERR_INVALID_PARAMETER_VALUE, "id", "an identifier");
> > + qerror_report(QERR_INVALID_PARAMETER_VALUE, id, "an identifier");
> > error_printf_unless_qmp("Identifiers consist of letters, digits, '-', 
> > '.', '_', starting with a letter.\n");
> > return NULL;
> > }
>
> No.
>
> QERR_INVALID_PARAMETER_VALUE's first argument is the parameter *name*,
> not the parameter *value*.
>
> In this case, the parameter name is "id". The variable id contains the
> parameter value.
>
> If you need a debugger to find the offending id=, then location
> information is lacking. Could you give an example where it's hard to
> find the offending parameter?
>
> Here's an example where it's easy to find:
>
> $ qemu-system-x86_64 -device e1000,id=.
> qemu-system-x86_64: -device e1000,id=.: Parameter 'id' expects an 
> identifier
> Identifiers consist of letters, digits, '-', '.', '_', starting with a 
> letter.

I had a call of qemu_chr_open with an id containing a space
(which looks better in the console display where the id is shown)
in my ar7 emulation. You can test this scenario using this patch:

--- a/vl.c
+++ b/vl.c
@@ -1700,7 +1700,7 @@ static int serial_parse(const char *devname)
         fprintf(stderr, "qemu: too many serial ports\n");
         exit(1);
     }
-    snprintf(label, sizeof(label), "serial%d", index);
+    snprintf(label, sizeof(label), "serial %d", index);
     serial_hds[index] = qemu_chr_open(label, devname, NULL);
     if (!serial_hds[index]) {
         fprintf(stderr, "qemu: could not open serial device '%s': %s\n",

It results in these error messages:

qemu: Parameter 'id' expects an identifier
Identifiers consist of letters, digits, '-', '.', '_', starting with a 
letter.
qemu: could not open serial device 'vc:80Cx24C': No such file or directory

The "location information" is indeed missing. For this kind of error,
an assertion would be better than an error message.