| Message ID | 20201123204522.675836-1-jonathantanmy@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [RFC,v2] usage: add trace2 entry upon warning() | expand |
Jonathan Tan <jonathantanmy@google.com> writes: > diff --git a/usage.c b/usage.c > index 06665823a2..1868a24f7a 100644 > --- a/usage.c > +++ b/usage.c > @@ -81,6 +81,12 @@ static void error_builtin(const char *err, va_list params) > > static void warn_builtin(const char *warn, va_list params) > { > + /* > + * We call this trace2 function first and expect it to va_copy 'params' > + * before using it (because an 'ap' can only be walked once). > + */ > + trace2_cmd_error_va(warn, params); > + > vreportf("warning: ", warn, params); Without the comment, this would have been a huge red sign. Given what the trace2 function does, I think cmd_error_va() has to do the va_copy()/va_end() dance somewhere in it, so from the caller's point of view, not having to va_copy()/va_end() is convenient and nice, but perhaps we can eventually (not today---we have the same issue with die_builtin() and error_builtin()) move the comment to the callee so that other people who are writing more callers do not have to rediscover what to do with "can va_lsit be used more than once?" issue. Perhaps like (I am not demonstrating the removal of dups): trace2.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git c/trace2.h w/trace2.h index b18bc5529c..10ba231122 100644 --- c/trace2.h +++ w/trace2.h @@ -116,6 +116,11 @@ int trace2_cmd_exit_fl(const char *file, int line, int code); * Emit an 'error' event. * * Write an error message to the TRACE2 targets. + * + * Note that the "va_list ap" the caller has is not touched, because + * it is fed to each of the TRACE2 targets, which must use va_copy() + * and use va_end() on the copy. The caller can still use ap it uses + * to call this funciton and and call va_end() on it when it is done. */ void trace2_cmd_error_va_fl(const char *file, int line, const char *fmt, va_list ap);
diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt index 6b6085585d..c65ffafc48 100644 --- a/Documentation/technical/api-trace2.txt +++ b/Documentation/technical/api-trace2.txt @@ -466,7 +466,7 @@ completed.) `"error"`:: This event is emitted when one of the `error()`, `die()`, - or `usage()` functions are called. + `warning()`, or `usage()` functions are called. + ------------ { diff --git a/usage.c b/usage.c index 06665823a2..1868a24f7a 100644 --- a/usage.c +++ b/usage.c @@ -81,6 +81,12 @@ static void error_builtin(const char *err, va_list params) static void warn_builtin(const char *warn, va_list params) { + /* + * We call this trace2 function first and expect it to va_copy 'params' + * before using it (because an 'ap' can only be walked once). + */ + trace2_cmd_error_va(warn, params); + vreportf("warning: ", warn, params); }
Emit a trace2 error event whenever warning() is called, just like when die(), error(), or usage() is called. This helps debugging issues that would trigger warnings but not errors. In particular, this might have helped debugging an issue I encountered with commit graphs at $DAYJOB [1]. There is a tradeoff between including potentially relevant messages and cluttering up the trace output produced. I think that warning() messages should be included in traces, because by its nature, Git is used over multiple invocations of the Git tool, and a failure (currently traced) in a Git invocation might be caused by an unexpected interaction in a previous Git invocation that only has a warning (currently untraced) as a symptom - as is the case in [1]. [1] https://lore.kernel.org/git/20200629220744.1054093-1-jonathantanmy@google.com/ Signed-off-by: Jonathan Tan <jonathantanmy@google.com> --- Whoops...I ran a compile for the first version but I sent the email out before looking at the results. The first version had a compile error, but this one should be fine. --- Documentation/technical/api-trace2.txt | 2 +- usage.c | 6 ++++++ 2 files changed, 7 insertions(+), 1 deletion(-)