trace: avoid conditional code compilation during option parsing

A default implementation for backend-specific routines is provided in
"trace/default.c", which backends can override by setting "trace_default=no" in
"configure".

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>

9 files changed, 72 insertions, 26 deletions

diff --git a/Makefile.objs b/Makefile.objs
index 4f8b0ed689..57a80e6130 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -379,6 +379,8 @@ ifneq ($(TRACE_BACKEND),dtrace)
 trace-obj-y = trace.o
 endif
 
+trace-nested-$(CONFIG_TRACE_DEFAULT) += default.o
+
 trace-nested-$(CONFIG_TRACE_SIMPLE) += simple.o
 trace-obj-$(CONFIG_TRACE_SIMPLE) += qemu-timer-common.o
 
diff --git a/configure b/configure
index ebf14eeb66..4f9b27ced4 100755
--- a/configure
+++ b/configure
@@ -3064,12 +3064,15 @@ bsd)
 ;;
 esac
 
+# use default implementation for tracing backend-specific routines
+trace_default=yes
 echo "TRACE_BACKEND=$trace_backend" >> $config_host_mak
 if test "$trace_backend" = "nop"; then
   echo "CONFIG_TRACE_NOP=y" >> $config_host_mak
 fi
 if test "$trace_backend" = "simple"; then
   echo "CONFIG_TRACE_SIMPLE=y" >> $config_host_mak
+  trace_default=no
   # Set the appropriate trace file.
   trace_file="\"$trace_file-\" FMT_pid"
 fi
@@ -3086,6 +3089,9 @@ if test "$trace_backend" = "dtrace"; then
   fi
 fi
 echo "CONFIG_TRACE_FILE=$trace_file" >> $config_host_mak
+if test "$trace_default" = "yes"; then
+  echo "CONFIG_TRACE_DEFAULT=y" >> $config_host_mak
+fi
 
 echo "TOOLS=$tools" >> $config_host_mak
 echo "ROMS=$roms" >> $config_host_mak
diff --git a/qemu-config.c b/qemu-config.c
index b64edc9730..4f3465d384 100644
--- a/qemu-config.c
+++ b/qemu-config.c
@@ -303,7 +303,6 @@ static QemuOptsList qemu_mon_opts = {
     },
 };
 
-#ifdef CONFIG_TRACE_SIMPLE
 static QemuOptsList qemu_trace_opts = {
     .name = "trace",
     .implied_opt_name = "trace",
@@ -316,7 +315,6 @@ static QemuOptsList qemu_trace_opts = {
         { /* end of list */ }
     },
 };
-#endif
 
 static QemuOptsList qemu_cpudef_opts = {
     .name = "cpudef",
@@ -517,9 +515,7 @@ static QemuOptsList *vm_config_groups[32] = {
     &qemu_global_opts,
     &qemu_mon_opts,
     &qemu_cpudef_opts,
-#ifdef CONFIG_TRACE_SIMPLE
     &qemu_trace_opts,
-#endif
     &qemu_option_rom_opts,
     &qemu_machine_opts,
     &qemu_boot_opts,
diff --git a/qemu-options.hx b/qemu-options.hx
index dcb00b7b9a..2d29933ab1 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2436,17 +2436,19 @@ Normally QEMU loads a configuration file from @var{sysconfdir}/qemu.conf and
 @var{sysconfdir}/target-@var{ARCH}.conf on startup.  The @code{-nodefconfig}
 option will prevent QEMU from loading these configuration files at startup.
 ETEXI
-#ifdef CONFIG_TRACE_SIMPLE
 DEF("trace", HAS_ARG, QEMU_OPTION_trace,
     "-trace\n"
     "                Specify a trace file to log traces to\n",
     QEMU_ARCH_ALL)
 STEXI
+HXCOMM This line is not accurate, as the option is backend-specific but HX does
+HXCOMM not support conditional compilation of text.
 @item -trace
 @findex -trace
 Specify a trace file to log output traces to.
+
+This option is available only when using the @var{simple} tracing backend.
 ETEXI
-#endif
 
 HXCOMM This is the last statement. Insert new options before this line!
 STEXI
diff --git a/trace/control.h b/trace/control.h
new file mode 100644
index 0000000000..bb54339258
--- /dev/null
+++ b/trace/control.h
@@ -0,0 +1,24 @@
+/*
+ * Interface for configuring and controlling the state of tracing events.
+ *
+ * Copyright (C) 2011 Lluís Vilanova <vilanova@ac.upc.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#ifndef TRACE_CONTROL_H
+#define TRACE_CONTROL_H
+
+#include <stdbool.h>
+
+
+/** Initialize the tracing backend.
+ *
+ * @file Name of trace output file; may be NULL.
+ *       Corresponds to commandline option "-trace file=...".
+ * @return Whether the backend could be successfully initialized.
+ */
+bool trace_backend_init(const char *file);
+
+#endif  /* TRACE_CONTROL_H */
diff --git a/trace/default.c b/trace/default.c
new file mode 100644
index 0000000000..42fdb6b6a4
--- /dev/null
+++ b/trace/default.c
@@ -0,0 +1,21 @@
+/*
+ * Default implementation for backend initialization from commandline.
+ *
+ * Copyright (C) 2011 Lluís Vilanova <vilanova@ac.upc.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "trace/control.h"
+
+
+bool trace_backend_init(const char *file)
+{
+    if (file) {
+        fprintf(stderr, "error: -trace file=...: "
+                "option not supported by the selected tracing backend\n");
+        return false;
+    }
+    return true;
+}
diff --git a/trace/simple.c b/trace/simple.c
index de355e9675..369e860305 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -16,6 +16,7 @@
 #include <pthread.h>
 #include "qemu-timer.h"
 #include "trace.h"
+#include "trace/control.h"
 
 /** Trace file header event ID */
 #define HEADER_EVENT_ID (~(uint64_t)0) /* avoids conflicting with TraceEventIDs */
@@ -330,7 +331,7 @@ void st_flush_trace_buffer(void)
     flush_trace_file(true);
 }
 
-bool st_init(const char *file)
+bool trace_backend_init(const char *file)
 {
     pthread_t thread;
     pthread_attr_t attr;
@@ -346,10 +347,11 @@ bool st_init(const char *file)
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 
     if (ret != 0) {
-        return false;
+        fprintf(stderr, "warning: unable to initialize simple trace backend\n");
+    } else {
+        atexit(st_flush_trace_buffer);
+        st_set_trace_file(file);
     }
 
-    atexit(st_flush_trace_buffer);
-    st_set_trace_file(file);
     return true;
 }
diff --git a/trace/simple.h b/trace/simple.h
index 77633ab68a..08b9a52146 100644
--- a/trace/simple.h
+++ b/trace/simple.h
@@ -15,7 +15,6 @@
 #include <stdbool.h>
 #include <stdio.h>
 
-#ifdef CONFIG_TRACE_SIMPLE
 typedef uint64_t TraceEventID;
 
 typedef struct {
@@ -37,12 +36,5 @@ void st_print_trace_file_status(FILE *stream, fprintf_function stream_printf);
 void st_set_trace_file_enabled(bool enable);
 bool st_set_trace_file(const char *file);
 void st_flush_trace_buffer(void);
-bool st_init(const char *file);
-#else
-static inline bool st_init(const char *file)
-{
-    return true;
-}
-#endif /* !CONFIG_TRACE_SIMPLE */
 
 #endif /* TRACE_SIMPLE_H */
diff --git a/vl.c b/vl.c
index 145d7384d8..60322b62a4 100644
--- a/vl.c
+++ b/vl.c
@@ -156,7 +156,7 @@ int main(int argc, char **argv)
 #include "slirp/libslirp.h"
 
 #include "trace.h"
-#include "trace/simple.h"
+#include "trace/control.h"
 #include "qemu-queue.h"
 #include "cpus.h"
 #include "arch_init.h"
@@ -2130,7 +2130,6 @@ int main(int argc, char **argv, char **envp)
     int show_vnc_port = 0;
 #endif
     int defconfig = 1;
-    const char *trace_file = NULL;
     const char *log_mask = NULL;
     const char *log_file = NULL;
     GMemVTable mem_trace = {
@@ -2138,6 +2137,7 @@ int main(int argc, char **argv, char **envp)
         .realloc = realloc_and_trace,
         .free = free_and_trace,
     };
+    const char *trace_file = NULL;
 
     atexit(qemu_run_exit_notifiers);
     error_set_progname(argv[0]);
@@ -2928,14 +2928,15 @@ int main(int argc, char **argv, char **envp)
                 }
                 xen_mode = XEN_ATTACH;
                 break;
-#ifdef CONFIG_TRACE_SIMPLE
             case QEMU_OPTION_trace:
+            {
                 opts = qemu_opts_parse(qemu_find_opts("trace"), optarg, 0);
-                if (opts) {
-                    trace_file = qemu_opt_get(opts, "file");
+                if (!opts) {
+                    exit(1);
                 }
+                trace_file = qemu_opt_get(opts, "file");
                 break;
-#endif
+            }
             case QEMU_OPTION_readconfig:
                 {
                     int ret = qemu_read_config_file(optarg);
@@ -2993,8 +2994,8 @@ int main(int argc, char **argv, char **envp)
         set_cpu_log(log_mask);
     }
 
-    if (!st_init(trace_file)) {
-        fprintf(stderr, "warning: unable to initialize simple trace backend\n");
+    if (!trace_backend_init(trace_file)) {
+        exit(1);
     }
 
     /* If no data_dir is specified then try to find it relative to the