* [PATCH] perf probe: Improve C++ support in arguments
@ 2025-12-05 12:36 Steinar H. Gunderson
2026-04-01 21:03 ` Ian Rogers
0 siblings, 1 reply; 4+ messages in thread
From: Steinar H. Gunderson @ 2025-12-05 12:36 UTC (permalink / raw)
To: acme; +Cc: linux-perf-users, linux-kernel, irogers, Steinar H. Gunderson
For purposes of specifying arguments in tracepoints, C++ classes
work exactly like structs, and C++ references work almost exactly
like pointers (they are dereferenced with . instead of ->).
However, they use different tags in DWARF, which means you cannot
use them in arguments.
Implement support for both, based on the existing struct and pointer
support. This allows us to to something like this in Chromium:
perf probe --exec content_shell --add 'PerformanceMark=\
_ZN5blink15PerformanceMark6CreateEPNS_11ScriptStateERKNS_12\
AtomicStringEPNS_22PerformanceMarkOptionsERNS_14ExceptionStateE \
mark_name.string_.impl_.ptr_'
even though mark_name is an class AtomicString&.
We don't support advanced C++ features, such as operator overloading.
Unfortunately, we also don't support C++-style strings where there
is a separate length field instead of null-termination. We also cannot
go past ptr_ in the example above (e.g. add ->length_), due to
unrelated DWARF issues.
Signed-off-by: Steinar H. Gunderson <sesse@google.com>
Cc: Ian Rogers <irogers@google.com>
---
tools/perf/util/annotate-data.c | 3 ++-
tools/perf/util/dwarf-aux.c | 13 ++++++++++---
tools/perf/util/probe-finder.c | 24 +++++++++++++++++-------
3 files changed, 29 insertions(+), 11 deletions(-)
diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 07cf9c334be0..d97b5fc61e6f 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -459,7 +459,8 @@ static bool is_pointer_type(Dwarf_Die *type_die)
{
int tag = dwarf_tag(type_die);
- return tag == DW_TAG_pointer_type || tag == DW_TAG_array_type;
+ return tag == DW_TAG_pointer_type || tag == DW_TAG_reference_type ||
+ tag == DW_TAG_array_type;
}
static bool is_compound_type(Dwarf_Die *type_die)
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 9267af204c7d..25bbc840d1a8 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1112,6 +1112,8 @@ int die_get_typename_from_type(Dwarf_Die *type_die, struct strbuf *buf)
tag = dwarf_tag(type_die);
if (tag == DW_TAG_pointer_type)
tmp = "*";
+ else if (tag == DW_TAG_reference_type)
+ tmp = "&";
else if (tag == DW_TAG_array_type)
tmp = "[]";
else if (tag == DW_TAG_subroutine_type) {
@@ -1124,6 +1126,8 @@ int die_get_typename_from_type(Dwarf_Die *type_die, struct strbuf *buf)
tmp = "union ";
else if (tag == DW_TAG_structure_type)
tmp = "struct ";
+ else if (tag == DW_TAG_class_type)
+ tmp = "class ";
else if (tag == DW_TAG_enumeration_type)
tmp = "enum ";
else if (name == NULL)
@@ -2065,7 +2069,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
tag = dwarf_tag(type_die);
/* If it's not a compound type, return the type directly */
- if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
+ if (tag != DW_TAG_structure_type && tag != DW_TAG_class_type &&
+ tag != DW_TAG_union_type) {
Dwarf_Word size;
if (dwarf_aggregate_size(type_die, &size) < 0)
@@ -2080,7 +2085,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
mb_type = *type_die;
/* TODO: Handle union types better? */
- while (tag == DW_TAG_structure_type || tag == DW_TAG_union_type) {
+ while (tag == DW_TAG_structure_type || tag == DW_TAG_class_type ||
+ tag == DW_TAG_union_type) {
member = die_find_child(&mb_type, __die_find_member_offset_cb,
(void *)(long)offset, die_mem);
if (member == NULL)
@@ -2091,7 +2097,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
tag = dwarf_tag(&mb_type);
- if (tag == DW_TAG_structure_type || tag == DW_TAG_union_type) {
+ if (tag == DW_TAG_structure_type || tag == DW_TAG_class_type ||
+ tag == DW_TAG_union_type) {
Dwarf_Word loc;
/* Update offset for the start of the member struct */
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 5ffd97ee4898..ca4734c75bba 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -360,12 +360,20 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
ref->offset += dwarf_bytesize(&type) * field->index;
ref->user_access = user_access;
goto next;
- } else if (tag == DW_TAG_pointer_type) {
+ } else if (tag == DW_TAG_pointer_type || tag == DW_TAG_reference_type) {
/* Check the pointer and dereference */
- if (!field->ref) {
- pr_err("Semantic error: %s must be referred by '->'\n",
- field->name);
- return -EINVAL;
+ if (tag == DW_TAG_pointer_type) {
+ if (!field->ref) {
+ pr_err("Semantic error: %s must be referred by '->'\n",
+ field->name);
+ return -EINVAL;
+ }
+ } else {
+ if (field->ref) {
+ pr_err("Semantic error: %s must be referred by '.'\n",
+ field->name);
+ return -EINVAL;
+ }
}
/* Get the type pointed by this pointer */
if (die_get_real_type(&type, &type) == NULL) {
@@ -374,7 +382,8 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
}
/* Verify it is a data structure */
tag = dwarf_tag(&type);
- if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
+ if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type &&
+ tag != DW_TAG_class_type) {
pr_warning("%s is not a data structure nor a union.\n",
varname);
return -EINVAL;
@@ -389,7 +398,8 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
*ref_ptr = ref;
} else {
/* Verify it is a data structure */
- if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
+ if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type &&
+ tag != DW_TAG_class_type) {
pr_warning("%s is not a data structure nor a union.\n",
varname);
return -EINVAL;
--
2.51.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] perf probe: Improve C++ support in arguments
2025-12-05 12:36 [PATCH] perf probe: Improve C++ support in arguments Steinar H. Gunderson
@ 2026-04-01 21:03 ` Ian Rogers
2026-04-01 21:11 ` Arnaldo Carvalho de Melo
0 siblings, 1 reply; 4+ messages in thread
From: Ian Rogers @ 2026-04-01 21:03 UTC (permalink / raw)
To: Steinar H. Gunderson, Namhyung Kim; +Cc: acme, linux-perf-users, linux-kernel
On Fri, Dec 5, 2025 at 4:36 AM Steinar H. Gunderson <sesse@google.com> wrote:
>
> For purposes of specifying arguments in tracepoints, C++ classes
> work exactly like structs, and C++ references work almost exactly
> like pointers (they are dereferenced with . instead of ->).
> However, they use different tags in DWARF, which means you cannot
> use them in arguments.
>
> Implement support for both, based on the existing struct and pointer
> support. This allows us to to something like this in Chromium:
>
> perf probe --exec content_shell --add 'PerformanceMark=\
> _ZN5blink15PerformanceMark6CreateEPNS_11ScriptStateERKNS_12\
> AtomicStringEPNS_22PerformanceMarkOptionsERNS_14ExceptionStateE \
> mark_name.string_.impl_.ptr_'
>
> even though mark_name is an class AtomicString&.
>
> We don't support advanced C++ features, such as operator overloading.
> Unfortunately, we also don't support C++-style strings where there
> is a separate length field instead of null-termination. We also cannot
> go past ptr_ in the example above (e.g. add ->length_), due to
> unrelated DWARF issues.
>
> Signed-off-by: Steinar H. Gunderson <sesse@google.com>
> Cc: Ian Rogers <irogers@google.com>
This change makes sense to me, Namhyung?
Thanks,
Ian
> ---
> tools/perf/util/annotate-data.c | 3 ++-
> tools/perf/util/dwarf-aux.c | 13 ++++++++++---
> tools/perf/util/probe-finder.c | 24 +++++++++++++++++-------
> 3 files changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
> index 07cf9c334be0..d97b5fc61e6f 100644
> --- a/tools/perf/util/annotate-data.c
> +++ b/tools/perf/util/annotate-data.c
> @@ -459,7 +459,8 @@ static bool is_pointer_type(Dwarf_Die *type_die)
> {
> int tag = dwarf_tag(type_die);
>
> - return tag == DW_TAG_pointer_type || tag == DW_TAG_array_type;
> + return tag == DW_TAG_pointer_type || tag == DW_TAG_reference_type ||
> + tag == DW_TAG_array_type;
> }
>
> static bool is_compound_type(Dwarf_Die *type_die)
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index 9267af204c7d..25bbc840d1a8 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -1112,6 +1112,8 @@ int die_get_typename_from_type(Dwarf_Die *type_die, struct strbuf *buf)
> tag = dwarf_tag(type_die);
> if (tag == DW_TAG_pointer_type)
> tmp = "*";
> + else if (tag == DW_TAG_reference_type)
> + tmp = "&";
> else if (tag == DW_TAG_array_type)
> tmp = "[]";
> else if (tag == DW_TAG_subroutine_type) {
> @@ -1124,6 +1126,8 @@ int die_get_typename_from_type(Dwarf_Die *type_die, struct strbuf *buf)
> tmp = "union ";
> else if (tag == DW_TAG_structure_type)
> tmp = "struct ";
> + else if (tag == DW_TAG_class_type)
> + tmp = "class ";
> else if (tag == DW_TAG_enumeration_type)
> tmp = "enum ";
> else if (name == NULL)
> @@ -2065,7 +2069,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
>
> tag = dwarf_tag(type_die);
> /* If it's not a compound type, return the type directly */
> - if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
> + if (tag != DW_TAG_structure_type && tag != DW_TAG_class_type &&
> + tag != DW_TAG_union_type) {
> Dwarf_Word size;
>
> if (dwarf_aggregate_size(type_die, &size) < 0)
> @@ -2080,7 +2085,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
>
> mb_type = *type_die;
> /* TODO: Handle union types better? */
> - while (tag == DW_TAG_structure_type || tag == DW_TAG_union_type) {
> + while (tag == DW_TAG_structure_type || tag == DW_TAG_class_type ||
> + tag == DW_TAG_union_type) {
> member = die_find_child(&mb_type, __die_find_member_offset_cb,
> (void *)(long)offset, die_mem);
> if (member == NULL)
> @@ -2091,7 +2097,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
>
> tag = dwarf_tag(&mb_type);
>
> - if (tag == DW_TAG_structure_type || tag == DW_TAG_union_type) {
> + if (tag == DW_TAG_structure_type || tag == DW_TAG_class_type ||
> + tag == DW_TAG_union_type) {
> Dwarf_Word loc;
>
> /* Update offset for the start of the member struct */
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 5ffd97ee4898..ca4734c75bba 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -360,12 +360,20 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
> ref->offset += dwarf_bytesize(&type) * field->index;
> ref->user_access = user_access;
> goto next;
> - } else if (tag == DW_TAG_pointer_type) {
> + } else if (tag == DW_TAG_pointer_type || tag == DW_TAG_reference_type) {
> /* Check the pointer and dereference */
> - if (!field->ref) {
> - pr_err("Semantic error: %s must be referred by '->'\n",
> - field->name);
> - return -EINVAL;
> + if (tag == DW_TAG_pointer_type) {
> + if (!field->ref) {
> + pr_err("Semantic error: %s must be referred by '->'\n",
> + field->name);
> + return -EINVAL;
> + }
> + } else {
> + if (field->ref) {
> + pr_err("Semantic error: %s must be referred by '.'\n",
> + field->name);
> + return -EINVAL;
> + }
> }
> /* Get the type pointed by this pointer */
> if (die_get_real_type(&type, &type) == NULL) {
> @@ -374,7 +382,8 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
> }
> /* Verify it is a data structure */
> tag = dwarf_tag(&type);
> - if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
> + if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type &&
> + tag != DW_TAG_class_type) {
> pr_warning("%s is not a data structure nor a union.\n",
> varname);
> return -EINVAL;
> @@ -389,7 +398,8 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
> *ref_ptr = ref;
> } else {
> /* Verify it is a data structure */
> - if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
> + if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type &&
> + tag != DW_TAG_class_type) {
> pr_warning("%s is not a data structure nor a union.\n",
> varname);
> return -EINVAL;
> --
> 2.51.0
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] perf probe: Improve C++ support in arguments
2026-04-01 21:03 ` Ian Rogers
@ 2026-04-01 21:11 ` Arnaldo Carvalho de Melo
2026-04-01 23:23 ` Namhyung Kim
0 siblings, 1 reply; 4+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-04-01 21:11 UTC (permalink / raw)
To: Ian Rogers
Cc: Steinar H. Gunderson, Namhyung Kim, linux-perf-users,
linux-kernel
On Wed, Apr 01, 2026 at 02:03:42PM -0700, Ian Rogers wrote:
> On Fri, Dec 5, 2025 at 4:36 AM Steinar H. Gunderson <sesse@google.com> wrote:
> >
> > For purposes of specifying arguments in tracepoints, C++ classes
> > work exactly like structs, and C++ references work almost exactly
> > like pointers (they are dereferenced with . instead of ->).
> > However, they use different tags in DWARF, which means you cannot
> > use them in arguments.
> >
> > Implement support for both, based on the existing struct and pointer
> > support. This allows us to to something like this in Chromium:
> >
> > perf probe --exec content_shell --add 'PerformanceMark=\
> > _ZN5blink15PerformanceMark6CreateEPNS_11ScriptStateERKNS_12\
> > AtomicStringEPNS_22PerformanceMarkOptionsERNS_14ExceptionStateE \
> > mark_name.string_.impl_.ptr_'
> >
> > even though mark_name is an class AtomicString&.
> >
> > We don't support advanced C++ features, such as operator overloading.
> > Unfortunately, we also don't support C++-style strings where there
> > is a separate length field instead of null-termination. We also cannot
> > go past ptr_ in the example above (e.g. add ->length_), due to
> > unrelated DWARF issues.
> >
> > Signed-off-by: Steinar H. Gunderson <sesse@google.com>
> > Cc: Ian Rogers <irogers@google.com>
>
> This change makes sense to me, Namhyung?
Agreed, and there are some other C++ specific (Go as well), like
DW_TAG_rvalue_reference_type, that we may want to support, also it would
be great to have some extra workload in 'perf test -w' to have a shell
testing this feature, no?
- Arnaldo
> Thanks,
> Ian
>
> > ---
> > tools/perf/util/annotate-data.c | 3 ++-
> > tools/perf/util/dwarf-aux.c | 13 ++++++++++---
> > tools/perf/util/probe-finder.c | 24 +++++++++++++++++-------
> > 3 files changed, 29 insertions(+), 11 deletions(-)
> >
> > diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
> > index 07cf9c334be0..d97b5fc61e6f 100644
> > --- a/tools/perf/util/annotate-data.c
> > +++ b/tools/perf/util/annotate-data.c
> > @@ -459,7 +459,8 @@ static bool is_pointer_type(Dwarf_Die *type_die)
> > {
> > int tag = dwarf_tag(type_die);
> >
> > - return tag == DW_TAG_pointer_type || tag == DW_TAG_array_type;
> > + return tag == DW_TAG_pointer_type || tag == DW_TAG_reference_type ||
> > + tag == DW_TAG_array_type;
> > }
> >
> > static bool is_compound_type(Dwarf_Die *type_die)
> > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> > index 9267af204c7d..25bbc840d1a8 100644
> > --- a/tools/perf/util/dwarf-aux.c
> > +++ b/tools/perf/util/dwarf-aux.c
> > @@ -1112,6 +1112,8 @@ int die_get_typename_from_type(Dwarf_Die *type_die, struct strbuf *buf)
> > tag = dwarf_tag(type_die);
> > if (tag == DW_TAG_pointer_type)
> > tmp = "*";
> > + else if (tag == DW_TAG_reference_type)
> > + tmp = "&";
> > else if (tag == DW_TAG_array_type)
> > tmp = "[]";
> > else if (tag == DW_TAG_subroutine_type) {
> > @@ -1124,6 +1126,8 @@ int die_get_typename_from_type(Dwarf_Die *type_die, struct strbuf *buf)
> > tmp = "union ";
> > else if (tag == DW_TAG_structure_type)
> > tmp = "struct ";
> > + else if (tag == DW_TAG_class_type)
> > + tmp = "class ";
> > else if (tag == DW_TAG_enumeration_type)
> > tmp = "enum ";
> > else if (name == NULL)
> > @@ -2065,7 +2069,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
> >
> > tag = dwarf_tag(type_die);
> > /* If it's not a compound type, return the type directly */
> > - if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
> > + if (tag != DW_TAG_structure_type && tag != DW_TAG_class_type &&
> > + tag != DW_TAG_union_type) {
> > Dwarf_Word size;
> >
> > if (dwarf_aggregate_size(type_die, &size) < 0)
> > @@ -2080,7 +2085,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
> >
> > mb_type = *type_die;
> > /* TODO: Handle union types better? */
> > - while (tag == DW_TAG_structure_type || tag == DW_TAG_union_type) {
> > + while (tag == DW_TAG_structure_type || tag == DW_TAG_class_type ||
> > + tag == DW_TAG_union_type) {
> > member = die_find_child(&mb_type, __die_find_member_offset_cb,
> > (void *)(long)offset, die_mem);
> > if (member == NULL)
> > @@ -2091,7 +2097,8 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
> >
> > tag = dwarf_tag(&mb_type);
> >
> > - if (tag == DW_TAG_structure_type || tag == DW_TAG_union_type) {
> > + if (tag == DW_TAG_structure_type || tag == DW_TAG_class_type ||
> > + tag == DW_TAG_union_type) {
> > Dwarf_Word loc;
> >
> > /* Update offset for the start of the member struct */
> > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > index 5ffd97ee4898..ca4734c75bba 100644
> > --- a/tools/perf/util/probe-finder.c
> > +++ b/tools/perf/util/probe-finder.c
> > @@ -360,12 +360,20 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
> > ref->offset += dwarf_bytesize(&type) * field->index;
> > ref->user_access = user_access;
> > goto next;
> > - } else if (tag == DW_TAG_pointer_type) {
> > + } else if (tag == DW_TAG_pointer_type || tag == DW_TAG_reference_type) {
> > /* Check the pointer and dereference */
> > - if (!field->ref) {
> > - pr_err("Semantic error: %s must be referred by '->'\n",
> > - field->name);
> > - return -EINVAL;
> > + if (tag == DW_TAG_pointer_type) {
> > + if (!field->ref) {
> > + pr_err("Semantic error: %s must be referred by '->'\n",
> > + field->name);
> > + return -EINVAL;
> > + }
> > + } else {
> > + if (field->ref) {
> > + pr_err("Semantic error: %s must be referred by '.'\n",
> > + field->name);
> > + return -EINVAL;
> > + }
> > }
> > /* Get the type pointed by this pointer */
> > if (die_get_real_type(&type, &type) == NULL) {
> > @@ -374,7 +382,8 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
> > }
> > /* Verify it is a data structure */
> > tag = dwarf_tag(&type);
> > - if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
> > + if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type &&
> > + tag != DW_TAG_class_type) {
> > pr_warning("%s is not a data structure nor a union.\n",
> > varname);
> > return -EINVAL;
> > @@ -389,7 +398,8 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
> > *ref_ptr = ref;
> > } else {
> > /* Verify it is a data structure */
> > - if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
> > + if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type &&
> > + tag != DW_TAG_class_type) {
> > pr_warning("%s is not a data structure nor a union.\n",
> > varname);
> > return -EINVAL;
> > --
> > 2.51.0
> >
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] perf probe: Improve C++ support in arguments
2026-04-01 21:11 ` Arnaldo Carvalho de Melo
@ 2026-04-01 23:23 ` Namhyung Kim
0 siblings, 0 replies; 4+ messages in thread
From: Namhyung Kim @ 2026-04-01 23:23 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo
Cc: Ian Rogers, Steinar H. Gunderson, linux-perf-users, linux-kernel
On Wed, Apr 01, 2026 at 06:11:16PM -0300, Arnaldo Carvalho de Melo wrote:
> On Wed, Apr 01, 2026 at 02:03:42PM -0700, Ian Rogers wrote:
> > On Fri, Dec 5, 2025 at 4:36 AM Steinar H. Gunderson <sesse@google.com> wrote:
> > >
> > > For purposes of specifying arguments in tracepoints, C++ classes
> > > work exactly like structs, and C++ references work almost exactly
> > > like pointers (they are dereferenced with . instead of ->).
> > > However, they use different tags in DWARF, which means you cannot
> > > use them in arguments.
> > >
> > > Implement support for both, based on the existing struct and pointer
> > > support. This allows us to to something like this in Chromium:
> > >
> > > perf probe --exec content_shell --add 'PerformanceMark=\
> > > _ZN5blink15PerformanceMark6CreateEPNS_11ScriptStateERKNS_12\
> > > AtomicStringEPNS_22PerformanceMarkOptionsERNS_14ExceptionStateE \
> > > mark_name.string_.impl_.ptr_'
> > >
> > > even though mark_name is an class AtomicString&.
> > >
> > > We don't support advanced C++ features, such as operator overloading.
> > > Unfortunately, we also don't support C++-style strings where there
> > > is a separate length field instead of null-termination. We also cannot
> > > go past ptr_ in the example above (e.g. add ->length_), due to
> > > unrelated DWARF issues.
> > >
> > > Signed-off-by: Steinar H. Gunderson <sesse@google.com>
> > > Cc: Ian Rogers <irogers@google.com>
> >
> > This change makes sense to me, Namhyung?
>
> Agreed, and there are some other C++ specific (Go as well), like
> DW_TAG_rvalue_reference_type, that we may want to support, also it would
> be great to have some extra workload in 'perf test -w' to have a shell
> testing this feature, no?
Yep, that would be great. I'm ok with the change but it needs to be
updated. Also I think we need a helper to check the compound types.
Thanks,
Namhyung
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-04-01 23:23 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-12-05 12:36 [PATCH] perf probe: Improve C++ support in arguments Steinar H. Gunderson
2026-04-01 21:03 ` Ian Rogers
2026-04-01 21:11 ` Arnaldo Carvalho de Melo
2026-04-01 23:23 ` Namhyung Kim
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox