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

["Daniel P. Berrangé" <berrange@redhat.com>]

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. 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.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/message.h         |  1 +
 qemu-options.hx                |  9 +++++++--
 system/vl.c                    | 11 ++++++++++-
 tests/unit/test-error-report.c |  5 +++--
 util/error-report.c            |  4 ----
 util/message.c                 | 10 +++++++++-
 6 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/include/qemu/message.h b/include/qemu/message.h
index cfc3c92648..b8518d06be 100644
--- a/include/qemu/message.h
+++ b/include/qemu/message.h
@@ -6,6 +6,7 @@
 enum QMessageFormatFlags {
     QMESSAGE_FORMAT_TIMESTAMP = (1 << 0),
     QMESSAGE_FORMAT_WORKLOAD_NAME = (1 << 1),
+    QMESSAGE_FORMAT_PROGRAM_NAME = (1 << 2),
 };
 
 /**
diff --git a/qemu-options.hx b/qemu-options.hx
index cdb7fa20c2..84dcbb0983 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -5515,13 +5515,15 @@ ERST
 
 DEF("msg", HAS_ARG, QEMU_OPTION_msg,
     "-msg [timestamp=on|off][,guest-name=on|off]\n"
+    "     [,program-name=on|off]\n"
     "                control error message format\n"
     "                timestamp=on enables timestamps (default: off)\n"
     "                guest-name=on enables guest name prefix but only if\n"
-    "                              -name guest option is set (default: off)\n",
+    "                              -name guest option is set (default: off)\n"
+    "                program-name=off disables program name prefix (default: on)\n",
     QEMU_ARCH_ALL)
 SRST
-``-msg [timestamp=on|off][,guest-name=on|off]``
+``-msg [timestamp=on|off][,guest-name=on|off][,program-name=on|off]``
     Control error message format.
 
     ``timestamp=on|off``
@@ -5530,6 +5532,9 @@ SRST
     ``guest-name=on|off``
         Prefix messages with guest name but only if -name guest option is set
         otherwise the option is ignored. Default is off.
+
+    ``program-name=on|off``
+        Prefix messages with the program name. Default is on.
 ERST
 
 DEF("dump-vmstate", HAS_ARG, QEMU_OPTION_dump_vmstate,
diff --git a/system/vl.c b/system/vl.c
index be5862e55e..3e79bf47e0 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -381,6 +381,12 @@ static QemuOptsList qemu_msg_opts = {
             .help = "Prepends guest name for error messages but only if "
                     "-name guest is set otherwise option is ignored\n",
         },
+        {
+            .name = "program-name",
+            .type = QEMU_OPT_BOOL,
+            .help = "Prepends program name for error messages (enabled "
+                    "by default)\n",
+        },
         { /* end of list */ }
     },
 };
@@ -819,13 +825,16 @@ static void realtime_init(void)
 
 static void configure_msg(QemuOpts *opts)
 {
-    int flags = 0;
+    int flags = QMESSAGE_FORMAT_PROGRAM_NAME;
     if (qemu_opt_get_bool(opts, "timestamp", false)) {
         flags |= QMESSAGE_FORMAT_TIMESTAMP;
     }
     if (qemu_opt_get_bool(opts, "guest-name", false)) {
         flags |= QMESSAGE_FORMAT_WORKLOAD_NAME;
     }
+    if (!qemu_opt_get_bool(opts, "program-name", true)) {
+        flags &= ~QMESSAGE_FORMAT_PROGRAM_NAME;
+    }
     qmessage_set_format(flags);
 }
 
diff --git a/tests/unit/test-error-report.c b/tests/unit/test-error-report.c
index 9c63019694..714eafc51e 100644
--- a/tests/unit/test-error-report.c
+++ b/tests/unit/test-error-report.c
@@ -47,7 +47,7 @@ test_error_report_loc(void)
     g_test_trap_subprocess(NULL, 0, 0);
     g_test_trap_assert_passed();
     g_test_trap_assert_stderr("\
-test-error-report:some-file.c:7717: test error1*\
+test-error-report: some-file.c:7717: test error1*\
 test-error-report: test error2*\
 ");
 }
@@ -90,7 +90,8 @@ static void
 test_error_report_timestamp(void)
 {
     if (g_test_subprocess()) {
-        qmessage_set_format(QMESSAGE_FORMAT_TIMESTAMP);
+        qmessage_set_format(QMESSAGE_FORMAT_TIMESTAMP |
+                            QMESSAGE_FORMAT_PROGRAM_NAME);
         warn_report("warn");
         error_report("err");
         return;
diff --git a/util/error-report.c b/util/error-report.c
index 3009b93c23..196d51618c 100644
--- a/util/error-report.c
+++ b/util/error-report.c
@@ -179,10 +179,6 @@ static void print_loc(Monitor *cur)
     int i;
     const char *const *argp;
 
-    if (!cur && g_get_prgname()) {
-        fprintf(stderr, "%s:", g_get_prgname());
-        sep = " ";
-    }
     switch (cur_loc->kind) {
     case LOC_CMDLINE:
         argp = cur_loc->ptr;
diff --git a/util/message.c b/util/message.c
index fb2c947153..dd01bf7462 100644
--- a/util/message.c
+++ b/util/message.c
@@ -5,7 +5,7 @@
 #include "qemu/message.h"
 #include "monitor/monitor.h"
 
-static int message_format;
+static int message_format = QMESSAGE_FORMAT_PROGRAM_NAME;
 static char *message_workloadname;
 
 void qmessage_set_format(int flags)
@@ -32,4 +32,12 @@ void qmessage_context_print(FILE *fp)
         fputs(message_workloadname, fp);
         fputc(' ', fp);
     }
+
+    if (message_format & QMESSAGE_FORMAT_PROGRAM_NAME) {
+        const char *pgnamestr = g_get_prgname();
+        if (pgnamestr) {
+            fputs(pgnamestr, fp);
+            fputs(": ", fp);
+        }
+    }
 }
-- 
2.53.0