Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Stephane Eranian]

On Fri, Oct 14, 2016 at 8:20 AM, Arnaldo Carvalho de Melo
 wrote:
> Em Fri, Oct 14, 2016 at 05:57:25AM -0700, Stephane Eranian escreveu:
>> On Fri, Oct 14, 2016 at 4:13 AM, Arnaldo Carvalho de Melo  
>> wrote:
>> > Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
>> >> Do we not need to release the memory for err_msg if the condition for
>> >> the 'if' statement evaluates to false?  Is it that we are going to
>> >> kill the process, so no need to release the memory?
>
>> > I guess that print_error() is called only when an error was returned
>> > somewhere, that ret parameter, then if there was no error
>> > (JVMTI_ERROR_NONE) in translating that numeric code to an string,
>> > err_msg, it can then be used with warnx() (the main purpose of
>> > print_error()) and then deallocated.
>> >
>> > For err != JVMTI_ERROR_NONE it silently goes back to the caller that
>> > expected it to print something.
>> >
>> > I.e. probably it should have an else clause, something like:
>> >
>> > if (err == JVMTI_ERROR_NONE) {
>> > warnx("%s failed with %s", msg, err_msg);
>> > (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
>> > } else {
>> > warnx("%s failed with an unknown error %d", msg, (int)ret);
>> > }
>> >
>> > Stephane?
>> I will fix all of the comments over the week-end. I am away from office 
>> today.
>
> I have almost all of them fixed, will fix this one too, if you agree
> with the analysis.
>
Ok, the proposed fix is correct.
Thanks for fixing issues.

Now, I am tracking down another issue with the injection of jitdump.
It seems something goes wrong with ordering and timestamps and some
valid jitdump samples are not symbolized. It is not clear what is
causing this yet. It may be the issue raised by Adrian a while ago
about the finished_round processing.


> - Arnaldo

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Stephane Eranian]

On Fri, Oct 14, 2016 at 8:20 AM, Arnaldo Carvalho de Melo
 wrote:
> Em Fri, Oct 14, 2016 at 05:57:25AM -0700, Stephane Eranian escreveu:
>> On Fri, Oct 14, 2016 at 4:13 AM, Arnaldo Carvalho de Melo  
>> wrote:
>> > Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
>> >> Do we not need to release the memory for err_msg if the condition for
>> >> the 'if' statement evaluates to false?  Is it that we are going to
>> >> kill the process, so no need to release the memory?
>
>> > I guess that print_error() is called only when an error was returned
>> > somewhere, that ret parameter, then if there was no error
>> > (JVMTI_ERROR_NONE) in translating that numeric code to an string,
>> > err_msg, it can then be used with warnx() (the main purpose of
>> > print_error()) and then deallocated.
>> >
>> > For err != JVMTI_ERROR_NONE it silently goes back to the caller that
>> > expected it to print something.
>> >
>> > I.e. probably it should have an else clause, something like:
>> >
>> > if (err == JVMTI_ERROR_NONE) {
>> > warnx("%s failed with %s", msg, err_msg);
>> > (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
>> > } else {
>> > warnx("%s failed with an unknown error %d", msg, (int)ret);
>> > }
>> >
>> > Stephane?
>> I will fix all of the comments over the week-end. I am away from office 
>> today.
>
> I have almost all of them fixed, will fix this one too, if you agree
> with the analysis.
>
Ok, the proposed fix is correct.
Thanks for fixing issues.

Now, I am tracking down another issue with the injection of jitdump.
It seems something goes wrong with ordering and timestamps and some
valid jitdump samples are not symbolized. It is not clear what is
causing this yet. It may be the issue raised by Adrian a while ago
about the finished_round processing.


> - Arnaldo

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Arnaldo Carvalho de Melo]

Em Fri, Oct 14, 2016 at 05:57:25AM -0700, Stephane Eranian escreveu:
> On Fri, Oct 14, 2016 at 4:13 AM, Arnaldo Carvalho de Melo  
> wrote:
> > Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
> >> Do we not need to release the memory for err_msg if the condition for
> >> the 'if' statement evaluates to false?  Is it that we are going to
> >> kill the process, so no need to release the memory?

> > I guess that print_error() is called only when an error was returned
> > somewhere, that ret parameter, then if there was no error
> > (JVMTI_ERROR_NONE) in translating that numeric code to an string,
> > err_msg, it can then be used with warnx() (the main purpose of
> > print_error()) and then deallocated.
> >
> > For err != JVMTI_ERROR_NONE it silently goes back to the caller that
> > expected it to print something.
> >
> > I.e. probably it should have an else clause, something like:
> >
> > if (err == JVMTI_ERROR_NONE) {
> > warnx("%s failed with %s", msg, err_msg);
> > (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
> > } else {
> > warnx("%s failed with an unknown error %d", msg, (int)ret);
> > }
> >
> > Stephane?
> I will fix all of the comments over the week-end. I am away from office today.

I have almost all of them fixed, will fix this one too, if you agree
with the analysis.

- Arnaldo

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Arnaldo Carvalho de Melo]

Em Fri, Oct 14, 2016 at 05:57:25AM -0700, Stephane Eranian escreveu:
> On Fri, Oct 14, 2016 at 4:13 AM, Arnaldo Carvalho de Melo  
> wrote:
> > Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
> >> Do we not need to release the memory for err_msg if the condition for
> >> the 'if' statement evaluates to false?  Is it that we are going to
> >> kill the process, so no need to release the memory?

> > I guess that print_error() is called only when an error was returned
> > somewhere, that ret parameter, then if there was no error
> > (JVMTI_ERROR_NONE) in translating that numeric code to an string,
> > err_msg, it can then be used with warnx() (the main purpose of
> > print_error()) and then deallocated.
> >
> > For err != JVMTI_ERROR_NONE it silently goes back to the caller that
> > expected it to print something.
> >
> > I.e. probably it should have an else clause, something like:
> >
> > if (err == JVMTI_ERROR_NONE) {
> > warnx("%s failed with %s", msg, err_msg);
> > (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
> > } else {
> > warnx("%s failed with an unknown error %d", msg, (int)ret);
> > }
> >
> > Stephane?
> I will fix all of the comments over the week-end. I am away from office today.

I have almost all of them fixed, will fix this one too, if you agree
with the analysis.

- Arnaldo

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Stephane Eranian]

On Fri, Oct 14, 2016 at 4:13 AM, Arnaldo Carvalho de Melo
 wrote:
> Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
>> On 13 October 2016 at 05:59, Stephane Eranian  wrote:
>> > +++ b/tools/perf/jvmti/libjvmti.c
>> > @@ -12,6 +12,17 @@
>> > +static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
>> > +{
>> > +   char *err_msg = NULL;
>> > +   jvmtiError err;
>> > +   err = (*jvmti)->GetErrorName(jvmti, ret, _msg);
>> > +   if (err == JVMTI_ERROR_NONE) {
>> > +   warnx("%s failed with %s", msg, err_msg);
>> > +   (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
>> > +   }
>> > +}
>>
>> Do we not need to release the memory for err_msg if the condition for
>> the 'if' statement evaluates to false?  Is it that we are going to
>> kill the process, so no need to release the memory?
>
> I guess that print_error() is called only when an error was returned
> somewhere, that ret parameter, then if there was no error
> (JVMTI_ERROR_NONE) in translating that numeric code to an string,
> err_msg, it can then be used with warnx() (the main purpose of
> print_error()) and then deallocated.
>
> For err != JVMTI_ERROR_NONE it silently goes back to the caller that
> expected it to print something.
>
> I.e. probably it should have an else clause, something like:
>
> if (err == JVMTI_ERROR_NONE) {
> warnx("%s failed with %s", msg, err_msg);
> (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
> } else {
> warnx("%s failed with an unknown error %d", msg, (int)ret);
> }
>
> Stephane?
>'I will fix all of the comments over the week-end. I am away from office today.

> - Arnaldo

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Stephane Eranian]

On Fri, Oct 14, 2016 at 4:13 AM, Arnaldo Carvalho de Melo
 wrote:
> Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
>> On 13 October 2016 at 05:59, Stephane Eranian  wrote:
>> > +++ b/tools/perf/jvmti/libjvmti.c
>> > @@ -12,6 +12,17 @@
>> > +static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
>> > +{
>> > +   char *err_msg = NULL;
>> > +   jvmtiError err;
>> > +   err = (*jvmti)->GetErrorName(jvmti, ret, _msg);
>> > +   if (err == JVMTI_ERROR_NONE) {
>> > +   warnx("%s failed with %s", msg, err_msg);
>> > +   (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
>> > +   }
>> > +}
>>
>> Do we not need to release the memory for err_msg if the condition for
>> the 'if' statement evaluates to false?  Is it that we are going to
>> kill the process, so no need to release the memory?
>
> I guess that print_error() is called only when an error was returned
> somewhere, that ret parameter, then if there was no error
> (JVMTI_ERROR_NONE) in translating that numeric code to an string,
> err_msg, it can then be used with warnx() (the main purpose of
> print_error()) and then deallocated.
>
> For err != JVMTI_ERROR_NONE it silently goes back to the caller that
> expected it to print something.
>
> I.e. probably it should have an else clause, something like:
>
> if (err == JVMTI_ERROR_NONE) {
> warnx("%s failed with %s", msg, err_msg);
> (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
> } else {
> warnx("%s failed with an unknown error %d", msg, (int)ret);
> }
>
> Stephane?
>'I will fix all of the comments over the week-end. I am away from office today.

> - Arnaldo

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Arnaldo Carvalho de Melo]

Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
> On 13 October 2016 at 05:59, Stephane Eranian  wrote:
> > +++ b/tools/perf/jvmti/libjvmti.c
> > @@ -12,6 +12,17 @@
> > +static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
> > +{
> > +   char *err_msg = NULL;
> > +   jvmtiError err;
> > +   err = (*jvmti)->GetErrorName(jvmti, ret, _msg);
> > +   if (err == JVMTI_ERROR_NONE) {
> > +   warnx("%s failed with %s", msg, err_msg);
> > +   (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
> > +   }
> > +}
> 
> Do we not need to release the memory for err_msg if the condition for
> the 'if' statement evaluates to false?  Is it that we are going to
> kill the process, so no need to release the memory?

I guess that print_error() is called only when an error was returned
somewhere, that ret parameter, then if there was no error
(JVMTI_ERROR_NONE) in translating that numeric code to an string,
err_msg, it can then be used with warnx() (the main purpose of
print_error()) and then deallocated.

For err != JVMTI_ERROR_NONE it silently goes back to the caller that
expected it to print something.

I.e. probably it should have an else clause, something like:

if (err == JVMTI_ERROR_NONE) {
warnx("%s failed with %s", msg, err_msg);
(*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
} else {
warnx("%s failed with an unknown error %d", msg, (int)ret);
}

Stephane?

- Arnaldo

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Arnaldo Carvalho de Melo]

Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
> On 13 October 2016 at 05:59, Stephane Eranian  wrote:
> > +++ b/tools/perf/jvmti/libjvmti.c
> > @@ -12,6 +12,17 @@
> > +static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
> > +{
> > +   char *err_msg = NULL;
> > +   jvmtiError err;
> > +   err = (*jvmti)->GetErrorName(jvmti, ret, _msg);
> > +   if (err == JVMTI_ERROR_NONE) {
> > +   warnx("%s failed with %s", msg, err_msg);
> > +   (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
> > +   }
> > +}
> 
> Do we not need to release the memory for err_msg if the condition for
> the 'if' statement evaluates to false?  Is it that we are going to
> kill the process, so no need to release the memory?

I guess that print_error() is called only when an error was returned
somewhere, that ret parameter, then if there was no error
(JVMTI_ERROR_NONE) in translating that numeric code to an string,
err_msg, it can then be used with warnx() (the main purpose of
print_error()) and then deallocated.

For err != JVMTI_ERROR_NONE it silently goes back to the caller that
expected it to print something.

I.e. probably it should have an else clause, something like:

if (err == JVMTI_ERROR_NONE) {
warnx("%s failed with %s", msg, err_msg);
(*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
} else {
warnx("%s failed with an unknown error %d", msg, (int)ret);
}

Stephane?

- Arnaldo

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Nilay Vaish]

On 13 October 2016 at 05:59, Stephane Eranian  wrote:
> diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c
> index ac12e4b91a92..2d9bc04b79a8 100644
> --- a/tools/perf/jvmti/libjvmti.c
> +++ b/tools/perf/jvmti/libjvmti.c
> @@ -12,6 +12,17 @@
>  static int has_line_numbers;
>  void *jvmti_agent;
>
> +static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
> +{
> +   char *err_msg = NULL;
> +   jvmtiError err;
> +   err = (*jvmti)->GetErrorName(jvmti, ret, _msg);
> +   if (err == JVMTI_ERROR_NONE) {
> +   warnx("%s failed with %s", msg, err_msg);
> +   (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
> +   }
> +}

Do we not need to release the memory for err_msg if the condition for
the 'if' statement evaluates to false?  Is it that we are going to
kill the process, so no need to release the memory?

--
Nilay

Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

[Nilay Vaish]

On 13 October 2016 at 05:59, Stephane Eranian  wrote:
> diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c
> index ac12e4b91a92..2d9bc04b79a8 100644
> --- a/tools/perf/jvmti/libjvmti.c
> +++ b/tools/perf/jvmti/libjvmti.c
> @@ -12,6 +12,17 @@
>  static int has_line_numbers;
>  void *jvmti_agent;
>
> +static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
> +{
> +   char *err_msg = NULL;
> +   jvmtiError err;
> +   err = (*jvmti)->GetErrorName(jvmti, ret, _msg);
> +   if (err == JVMTI_ERROR_NONE) {
> +   warnx("%s failed with %s", msg, err_msg);
> +   (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
> +   }
> +}

Do we not need to release the memory for err_msg if the condition for
the 'if' statement evaluates to false?  Is it that we are going to
kill the process, so no need to release the memory?

--
Nilay

[PATCH 1/9] perf/jit: improve error messages from JVMTI

[Stephane Eranian]

This patch improves the usefulness of error messages
generated by the JVMTI interfac.e This can help identify
the root cause of a problem by printing the actual error
code. The patch adds a new helper function called print_error().

Signed-off-by: Stephane Eranian 
---
 tools/perf/jvmti/libjvmti.c | 37 +++--
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c
index ac12e4b91a92..2d9bc04b79a8 100644
--- a/tools/perf/jvmti/libjvmti.c
+++ b/tools/perf/jvmti/libjvmti.c
@@ -12,6 +12,17 @@
 static int has_line_numbers;
 void *jvmti_agent;
 
+static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
+{
+   char *err_msg = NULL;
+   jvmtiError err;
+   err = (*jvmti)->GetErrorName(jvmti, ret, _msg);
+   if (err == JVMTI_ERROR_NONE) {
+   warnx("%s failed with %s", msg, err_msg);
+   (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
+   }
+}
+
 static jvmtiError
 do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
jvmti_line_info_t *tab, jint *nr)
@@ -22,8 +33,10 @@ do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, 
jint bci,
jvmtiError ret;
 
ret = (*jvmti)->GetLineNumberTable(jvmti, m, _lines, _tab);
-   if (ret != JVMTI_ERROR_NONE)
+   if (ret != JVMTI_ERROR_NONE) {
+   print_error(jvmti, "GetLineNumberTable", ret);
return ret;
+   }
 
for (i = 0; i < nr_lines; i++) {
if (loc_tab[i].start_location < bci) {
@@ -71,6 +84,8 @@ get_line_numbers(jvmtiEnv *jvmti, const void *compile_info, 
jvmti_line_info_t **
/* free what was allocated for nothing 
*/
(*jvmti)->Deallocate(jvmti, (unsigned 
char *)lne);
nr_total += (int)nr;
+   } else {
+   print_error(jvmti, 
"GetLineNumberTable", ret);
}
}
}
@@ -130,7 +145,7 @@ compiled_method_load_cb(jvmtiEnv *jvmti,
ret = (*jvmti)->GetMethodDeclaringClass(jvmti, method,
_class);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: cannot get declaring class");
+   print_error(jvmti, "GetMethodDeclaringClass", ret);
return;
}
 
@@ -144,21 +159,21 @@ compiled_method_load_cb(jvmtiEnv *jvmti,
 
ret = (*jvmti)->GetSourceFileName(jvmti, decl_class, _name);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: cannot get source filename ret=%d", ret);
+   print_error(jvmti, "GetSourceFileName", ret);
goto error;
}
 
ret = (*jvmti)->GetClassSignature(jvmti, decl_class,
  _sign, NULL);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: getclassignature failed");
+   print_error(jvmti, "GetClassSignature", ret);
goto error;
}
 
ret = (*jvmti)->GetMethodName(jvmti, method, _name,
  _sign, NULL);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: failed getmethodname");
+   print_error(jvmti, "GetMethodName", ret);
goto error;
}
 
@@ -253,7 +268,7 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved 
__unused)
 
ret = (*jvmti)->AddCapabilities(jvmti, );
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: acquire compiled_method capability failed");
+   print_error(jvmti, "AddCapabilities", ret);
return -1;
}
ret = (*jvmti)->GetJLocationFormat(jvmti, );
@@ -264,7 +279,9 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved 
__unused)
ret = (*jvmti)->AddCapabilities(jvmti, );
 if (ret == JVMTI_ERROR_NONE)
 has_line_numbers = 1;
-}
+} else if (ret != JVMTI_ERROR_NONE)
+   print_error(jvmti, "GetJLocationFormat", ret);
+
 
memset(, 0, sizeof(cb));
 
@@ -273,21 +290,21 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved 
__unused)
 
ret = (*jvmti)->SetEventCallbacks(jvmti, , sizeof(cb));
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: cannot set event callbacks");
+   print_error(jvmti, "SetEventCallbacks", ret);
return -1;
}
 
ret = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
JVMTI_EVENT_COMPILED_METHOD_LOAD, NULL);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: setnotification failed for method_load");
+   print_error(jvmti, 

[PATCH 1/9] perf/jit: improve error messages from JVMTI

[Stephane Eranian]

This patch improves the usefulness of error messages
generated by the JVMTI interfac.e This can help identify
the root cause of a problem by printing the actual error
code. The patch adds a new helper function called print_error().

Signed-off-by: Stephane Eranian 
---
 tools/perf/jvmti/libjvmti.c | 37 +++--
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c
index ac12e4b91a92..2d9bc04b79a8 100644
--- a/tools/perf/jvmti/libjvmti.c
+++ b/tools/perf/jvmti/libjvmti.c
@@ -12,6 +12,17 @@
 static int has_line_numbers;
 void *jvmti_agent;
 
+static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
+{
+   char *err_msg = NULL;
+   jvmtiError err;
+   err = (*jvmti)->GetErrorName(jvmti, ret, _msg);
+   if (err == JVMTI_ERROR_NONE) {
+   warnx("%s failed with %s", msg, err_msg);
+   (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
+   }
+}
+
 static jvmtiError
 do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
jvmti_line_info_t *tab, jint *nr)
@@ -22,8 +33,10 @@ do_get_line_numbers(jvmtiEnv *jvmti, void *pc, jmethodID m, 
jint bci,
jvmtiError ret;
 
ret = (*jvmti)->GetLineNumberTable(jvmti, m, _lines, _tab);
-   if (ret != JVMTI_ERROR_NONE)
+   if (ret != JVMTI_ERROR_NONE) {
+   print_error(jvmti, "GetLineNumberTable", ret);
return ret;
+   }
 
for (i = 0; i < nr_lines; i++) {
if (loc_tab[i].start_location < bci) {
@@ -71,6 +84,8 @@ get_line_numbers(jvmtiEnv *jvmti, const void *compile_info, 
jvmti_line_info_t **
/* free what was allocated for nothing 
*/
(*jvmti)->Deallocate(jvmti, (unsigned 
char *)lne);
nr_total += (int)nr;
+   } else {
+   print_error(jvmti, 
"GetLineNumberTable", ret);
}
}
}
@@ -130,7 +145,7 @@ compiled_method_load_cb(jvmtiEnv *jvmti,
ret = (*jvmti)->GetMethodDeclaringClass(jvmti, method,
_class);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: cannot get declaring class");
+   print_error(jvmti, "GetMethodDeclaringClass", ret);
return;
}
 
@@ -144,21 +159,21 @@ compiled_method_load_cb(jvmtiEnv *jvmti,
 
ret = (*jvmti)->GetSourceFileName(jvmti, decl_class, _name);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: cannot get source filename ret=%d", ret);
+   print_error(jvmti, "GetSourceFileName", ret);
goto error;
}
 
ret = (*jvmti)->GetClassSignature(jvmti, decl_class,
  _sign, NULL);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: getclassignature failed");
+   print_error(jvmti, "GetClassSignature", ret);
goto error;
}
 
ret = (*jvmti)->GetMethodName(jvmti, method, _name,
  _sign, NULL);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: failed getmethodname");
+   print_error(jvmti, "GetMethodName", ret);
goto error;
}
 
@@ -253,7 +268,7 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved 
__unused)
 
ret = (*jvmti)->AddCapabilities(jvmti, );
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: acquire compiled_method capability failed");
+   print_error(jvmti, "AddCapabilities", ret);
return -1;
}
ret = (*jvmti)->GetJLocationFormat(jvmti, );
@@ -264,7 +279,9 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved 
__unused)
ret = (*jvmti)->AddCapabilities(jvmti, );
 if (ret == JVMTI_ERROR_NONE)
 has_line_numbers = 1;
-}
+} else if (ret != JVMTI_ERROR_NONE)
+   print_error(jvmti, "GetJLocationFormat", ret);
+
 
memset(, 0, sizeof(cb));
 
@@ -273,21 +290,21 @@ Agent_OnLoad(JavaVM *jvm, char *options, void *reserved 
__unused)
 
ret = (*jvmti)->SetEventCallbacks(jvmti, , sizeof(cb));
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: cannot set event callbacks");
+   print_error(jvmti, "SetEventCallbacks", ret);
return -1;
}
 
ret = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
JVMTI_EVENT_COMPILED_METHOD_LOAD, NULL);
if (ret != JVMTI_ERROR_NONE) {
-   warnx("jvmti: setnotification failed for method_load");
+   print_error(jvmti, "SetEventNotificationMode(METHOD_LOAD)", 
ret);