[PATCH v2 1/1] trace2: NULL is not allowed for va_list

[PATCH v2 1/1] trace2: NULL is not allowed for va_list

[tboegi]

From: Torsten Bögershausen <tboegi@web.de>

Some compilers don't allow NULL to be passed for a va_list,
and e.g. "gcc (Raspbian 6.3.0-18+rpi1+deb9u1) 6.3.0 20170516"
errors out like this:
 trace2/tr2_tgt_event.c:193:18:
   error: invalid operands to binary &&
   (have ‘int’ and ‘va_list {aka __va_list}’)
    if (fmt && *fmt && ap) {
                       ^^
I couldn't find any hints that va_list and pointers can be mixed,
and no hints that they can't either. Morten Welinder comments:

"C99, Section 7.15, simply says that va_list "is an object type suitable for
holding information needed by the macros va_start, va_end, and
va_copy". So clearly not guaranteed to be mixable with pointers...

The portable solution is to use "va_list" everywhere in the callchain.
As a consequence, both trace2_region_enter_fl() and trace2_region_leave_fl()
now take a variable argument list.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
---
 trace2.c                | 15 +++++++++++----
 trace2.h                |  4 ++--
 trace2/tr2_tgt_event.c  |  2 +-
 trace2/tr2_tgt_normal.c |  2 +-
 trace2/tr2_tgt_perf.c   |  2 +-
 5 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/trace2.c b/trace2.c
index ccccd4ef09..8bbad56887 100644
--- a/trace2.c
+++ b/trace2.c
@@ -548,10 +548,14 @@ void trace2_region_enter_printf_va_fl(const char *file, int line,
 }

 void trace2_region_enter_fl(const char *file, int line, const char *category,
-			    const char *label, const struct repository *repo)
+			    const char *label, const struct repository *repo, ...)
 {
+	va_list ap;
+	va_start(ap, repo);
 	trace2_region_enter_printf_va_fl(file, line, category, label, repo,
-					 NULL, NULL);
+					 NULL, ap);
+	va_end(ap);
+
 }

 void trace2_region_enter_printf_fl(const char *file, int line,
@@ -621,10 +625,13 @@ void trace2_region_leave_printf_va_fl(const char *file, int line,
 }

 void trace2_region_leave_fl(const char *file, int line, const char *category,
-			    const char *label, const struct repository *repo)
+			    const char *label, const struct repository *repo, ...)
 {
+	va_list ap;
+	va_start(ap, repo);
 	trace2_region_leave_printf_va_fl(file, line, category, label, repo,
-					 NULL, NULL);
+					 NULL, ap);
+	va_end(ap);
 }

 void trace2_region_leave_printf_fl(const char *file, int line,
diff --git a/trace2.h b/trace2.h
index ae5020d0e6..b330a54a89 100644
--- a/trace2.h
+++ b/trace2.h
@@ -238,7 +238,7 @@ void trace2_def_repo_fl(const char *file, int line, struct repository *repo);
  * on this thread.
  */
 void trace2_region_enter_fl(const char *file, int line, const char *category,
-			    const char *label, const struct repository *repo);
+			    const char *label, const struct repository *repo, ...);

 #define trace2_region_enter(category, label, repo) \
 	trace2_region_enter_fl(__FILE__, __LINE__, (category), (label), (repo))
@@ -278,7 +278,7 @@ void trace2_region_enter_printf(const char *category, const char *label,
  * in this nesting level.
  */
 void trace2_region_leave_fl(const char *file, int line, const char *category,
-			    const char *label, const struct repository *repo);
+			    const char *label, const struct repository *repo, ...);

 #define trace2_region_leave(category, label, repo) \
 	trace2_region_leave_fl(__FILE__, __LINE__, (category), (label), (repo))
diff --git a/trace2/tr2_tgt_event.c b/trace2/tr2_tgt_event.c
index 107cb5317d..1cf4f62441 100644
--- a/trace2/tr2_tgt_event.c
+++ b/trace2/tr2_tgt_event.c
@@ -190,7 +190,7 @@ static void fn_atexit(uint64_t us_elapsed_absolute, int code)
 static void maybe_add_string_va(struct json_writer *jw, const char *field_name,
 				const char *fmt, va_list ap)
 {
-	if (fmt && *fmt && ap) {
+	if (fmt && *fmt) {
 		va_list copy_ap;
 		struct strbuf buf = STRBUF_INIT;

diff --git a/trace2/tr2_tgt_normal.c b/trace2/tr2_tgt_normal.c
index 547183d5b6..1a07d70abd 100644
--- a/trace2/tr2_tgt_normal.c
+++ b/trace2/tr2_tgt_normal.c
@@ -126,7 +126,7 @@ static void fn_atexit(uint64_t us_elapsed_absolute, int code)
 static void maybe_append_string_va(struct strbuf *buf, const char *fmt,
 				   va_list ap)
 {
-	if (fmt && *fmt && ap) {
+	if (fmt && *fmt) {
 		va_list copy_ap;

 		va_copy(copy_ap, ap);
diff --git a/trace2/tr2_tgt_perf.c b/trace2/tr2_tgt_perf.c
index f0746fcf86..2a866d701b 100644
--- a/trace2/tr2_tgt_perf.c
+++ b/trace2/tr2_tgt_perf.c
@@ -211,7 +211,7 @@ static void fn_atexit(uint64_t us_elapsed_absolute, int code)
 static void maybe_append_string_va(struct strbuf *buf, const char *fmt,
 				   va_list ap)
 {
-	if (fmt && *fmt && ap) {
+	if (fmt && *fmt) {
 		va_list copy_ap;

 		va_copy(copy_ap, ap);
--
2.21.0.135.g6e0cc67761

Re: [PATCH v2 1/1] trace2: NULL is not allowed for va_list

[Jeff Hostetler]

On 3/19/2019 1:13 PM, tboegi@web.de wrote:
> From: Torsten Bögershausen <tboegi@web.de>
> 
> Some compilers don't allow NULL to be passed for a va_list,
> and e.g. "gcc (Raspbian 6.3.0-18+rpi1+deb9u1) 6.3.0 20170516"
> errors out like this:
>   trace2/tr2_tgt_event.c:193:18:
>     error: invalid operands to binary &&
>     (have ‘int’ and ‘va_list {aka __va_list}’)
>      if (fmt && *fmt && ap) {
>                         ^^
> I couldn't find any hints that va_list and pointers can be mixed,
> and no hints that they can't either. Morten Welinder comments:
> 
> "C99, Section 7.15, simply says that va_list "is an object type suitable for
> holding information needed by the macros va_start, va_end, and
> va_copy". So clearly not guaranteed to be mixable with pointers...
> 
> The portable solution is to use "va_list" everywhere in the callchain.
> As a consequence, both trace2_region_enter_fl() and trace2_region_leave_fl()
> now take a variable argument list.
> 
> Signed-off-by: Torsten Bögershausen <tboegi@web.de>

Looks good.  Thanks for tracking this down.
Jeff


Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>