Re: [PATCH v6 25/27] util: add support for formatting a program name in messages

On Thu, Feb 19, 2026 at 11:08:45AM +0100, Markus Armbruster wrote:
> Daniel P. Berrangé <[email protected]> writes:
> 
> > The error_report function can include the program name in any
> > messages it prints. The qemu_log function has no equivalent
> > behaviour.
> >
> > This introduces support for a "program name" in the new
> > messages API, which will be included by default for all
> > binaries.
> >
> > This change tweaks the output of the error_report function,
> > adding a space between the program name and the location
> > info.
> 
> Why?

Looking again, arguably that is fixing a pre-existing bug

The current code is:

    if (!monitor_cur() && g_get_prgname()) {
        error_printf("%s:", g_get_prgname());
        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) {
            error_printf("%d:", cur_loc->num);
        }
        error_printf(" ");
        break;
    default:
        error_printf("%s", sep);
    }


Notice how we honour "sep" for LOC_CMDLINE but ignore
it for LOC_FILE.

With the program name printing moved out into a separate
function, the space is always printed. No change for
LOC_CMDLINE, but new whitespace for LOC_FILE.

Should have changed this in a separate patch.

> >       The qemu_log function will gain the program name. This
> > can be easily seen with the 'log' trace backend, and how it
> > is now more closely matching error_report output.
> >
> > Before:
> >
> >   # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
> >   qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x5584e13937f0 dir=fish
> >   qcrypto_tls_creds_get_path TLS creds path creds=0x5584e13937f0 filename=ca-cert.pem path=<none>
> >   qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory
> >
> > After:
> >
> >   # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
> >   qemu-system-x86_64: qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x5584e13937f0 dir=fish
> >   qemu-system-x86_64: qcrypto_tls_creds_get_path TLS creds path creds=0x5584e13937f0 filename=ca-cert.pem path=<none>
> >   qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory
> >
> > When adding this the '-msg program-name=on|off' option is
> > introduced, so that the program name (which is enabled by
> > default) can be supressed if desired. This could be useful
> > if '-msg guest-name=on' is being used as a more informative
> > identifier.
> 
> Separate patch?

It is a bit of a borderline decision, but I felt the knob to turn it
off should be in the same patch that force enables it.

> > Reviewed-by: Richard Henderson <[email protected]>
> > Signed-off-by: Daniel P. Berrangé <[email protected]>

With regards,
Daniel
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