[Qemu-devel] [PATCH 2/4] trace: allow PRI*64 at beginning and ending of format string

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

The tracetool parser only picks up PRI*64 and other format string macros
when enclosed between double quoted strings.  Lift this restriction by
extracting everything after the closing ')' as the format string:

  cpu_set_apic_base(uint64_t val) "%016"PRIx64
                                  ^^        ^^

One trick here: it turns out that backslashes in the format string like
"\n" were being interpreted by echo(1).  Fix this by using the POSIX
printf(1) command instead.  Although it normally does not make sense to
include backslashes in trace event format strings, an injected newline
causes tracetool to emit a broken header file and I want to eliminate
cases where broken output is emitted, even if the input was bad.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 docs/tracing.txt  |    5 +----
 scripts/tracetool |   20 +++++++++++++-------
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/docs/tracing.txt b/docs/tracing.txt
index e130a61..2c33a62 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -75,10 +75,7 @@ Trace events should use types as follows:
 
 Format strings should reflect the types defined in the trace event.  Take
 special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
-respectively.  This ensures portability between 32- and 64-bit platforms.  Note
-that format strings must begin and end with double quotes.  When using
-portability macros, ensure they are preceded and followed by double quotes:
-"value %"PRIx64"".
+respectively.  This ensures portability between 32- and 64-bit platforms.
 
 === Hints for adding new trace events ===
 
diff --git a/scripts/tracetool b/scripts/tracetool
index 743d246..4c9951d 100755
--- a/scripts/tracetool
+++ b/scripts/tracetool
@@ -40,6 +40,15 @@ EOF
     exit 1
 }
 
+# Print a line without interpreting backslash escapes
+#
+# The built-in echo command may interpret backslash escapes without an option
+# to disable this behavior.
+puts()
+{
+    printf "%s\n" "$1"
+}
+
 # Get the name of a trace event
 get_name()
 {
@@ -111,13 +120,10 @@ get_argc()
     echo $argc
 }
 
-# Get the format string for a trace event
+# Get the format string including double quotes for a trace event
 get_fmt()
 {
-    local fmt
-    fmt=${1#*\"}
-    fmt=${fmt%\"*}
-    echo "$fmt"
+    puts "${1#*)}"
 }
 
 linetoh_begin_nop()
@@ -266,7 +272,7 @@ linetoh_stderr()
 static inline void trace_$name($args)
 {
     if (trace_list[$stderr_event_num].state != 0) {
-        fprintf(stderr, "$name $fmt\n" $argnames);
+        fprintf(stderr, "$name " $fmt "\n" $argnames);
     }
 }
 EOF
@@ -366,7 +372,7 @@ DEFINE_TRACE(ust_$name);
 
 static void ust_${name}_probe($args)
 {
-    trace_mark(ust, $name, "$fmt"$argnames);
+    trace_mark(ust, $name, $fmt$argnames);
 }
 EOF
 
-- 
1.7.5.4