<> characters in C++ types get munged

[tavianator]

C++ template types have lots of <s and >s in them. But they get filtered out by stackcollapse-perf.pl (and possibly others, didn't check), and the resulting SVG has things like

std::vectorint, std::allocatorint ::push_back

instead of

std::vector<int, std::allocator<int> >::push_back

The following patch fixes this, but I assume has unintended consequences:

diff --git a/flamegraph.pl b/flamegraph.pl
index def5ed0..ede4514 100755
--- a/flamegraph.pl
+++ b/flamegraph.pl
@@ -517,8 +517,6 @@ foreach (sort @Data) {
                $maxdelta = abs($delta) if abs($delta) > $maxdelta;
        }

-       $stack =~ tr/<>/()/;
-
        # merge frames and populate %Node:
        $last = flow($last, [ '', split ";", $stack ], $time, $delta);

diff --git a/stackcollapse-perf.pl b/stackcollapse-perf.pl
index 16b47f0..fdca6cc 100755
--- a/stackcollapse-perf.pl
+++ b/stackcollapse-perf.pl
@@ -135,7 +135,6 @@ foreach (<STDIN>) {
                next if $func =~ /^\(/;         # skip process names
                if ($tidy_generic) {
                        $func =~ s/;/:/g;
-                       $func =~ tr/<>//d;
                        $func =~ s/\(.*//;
                        # now tidy this horrible thing:
                        # 13a80b608e0a RegExp:[&<>\"\'] (/tmp/perf-7539.map)

[tavianator]

Also, demangled C++ types can have (anonymous namespace):: in them, which makes the $func =~ s/\(.*//; line suspect as well.

[borellim]

Fixing this issue would be very useful. It's quite hard to read templated functions at the moment.

Thank you @tavianator for the patch: it appears to turn angle brackets into round brackets, which is a nice temporary solution.

Even better, in my opinion, would be to add a switch to completely strip template parameters: this would shorten the names, and the loss of information would be negligible in many cases. 'gprof2dot' can do it with the '-s' option.

@brendangregg , any input on this?

[brendangregg]

This might have been fixed since the issue was filed, as I see flamegraph.pl currently has:

   572      # clean up SVG breaking characters:
   573      $stack =~ tr/<>/()/;

[borellim]

So, I was wrong: the angle brackets are turned into parentheses exactly by the line that you mentioned. Unfortunately (at least with perf) they don't actually show up unless you also remove line 216 in stackcollapse-perf.pl:

$func =~ tr/<>//d;

In my tests, removing this line shows them as parentheses, while also removing line 573 of flamegraph.pl correctly shows them as angle brackets. I didn't try with input from other profilers, though.

My suggestion to add a switch to strip the template parameters still stands; I'm using a sed script now, and I find the output much clearer.

Thanks a lot.

[Yamakaky]

I have a similar issue with Rust, with has the same syntax that C++ for the generics. <...> gets turned into (). If I remove the $stack =~ tr/<>/()/; line mentioned above, the <> are kept as expected. From the comments it seems like it's to protect SVG, but I don't have any issues with this fix.

[Yamakaky]

The <> characters are xml encoded, so I don't think it's a problem https://github.com/brendangregg/FlameGraph/blob/master/flamegraph.pl#L1022-L1023

[brendangregg]

I just pushed the patch earlier (thanks), and this is hopefully fixed.

I also added a new test file, test/perf-js-stacks-01.txt, and the corresponding test/results files, which are checked by the test.sh program. This new test file has many <> chars in.

If you have some rust or C++ profile output in particular that should behave, it would be good to add sample output (you may need to redact it) in a similar way under test/. It can be just a few stacks (like the one I just added).

Eg, to fix the "(anonymous namespace)::" issue it's going to be helpful to have a variety of output in test/ so we can check what regexp is going to work...

[Yamakaky]

I have a rust example. What do you want exactly? perf.data + output svg?

[brendangregg]

Just the "perf script" output, and you can edit/truncate it down as much as you like. See under test/ -- some are the full output (including header), some are just a couple of stacks. You can also just create a new ticket with "rust example" and paste the "perf script" output in and I'll add it to tests. thanks!

[Yamakaky]

in a PR?

[brendangregg]

either a PR or just pasted in a ticket is fine

[Yamakaky]

Just did #109