From: "fche at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug translator/18431] New: runtime function overloading facility
Date: Tue, 19 May 2015 15:46:00 -0000 [thread overview]
Message-ID: <bug-18431-6586@http.sourceware.org/bugzilla/> (raw)
https://sourceware.org/bugzilla/show_bug.cgi?id=18431
Bug ID: 18431
Summary: runtime function overloading facility
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: translator
Assignee: systemtap at sourceware dot org
Reporter: fche at redhat dot com
Target Milestone: ---
It turns out to be necessary to have a facility that allows end-user scripts to
call generic functions like jstack(), while multiple alternative
implementations available in the tapset library. The method of choosing
between the alternatives must be done at run-time (since it's run-time state
such as "which VM is this thread running in?" that decides), so we're talking
about a control-flow extension rather than translate-time processing like c++
overloading.
Possible syntax at call site: foo() - i.e., no visible change.
Possible syntax at definitions:
function foo () {
...
... if (condition) next; ...
...
}
Possible semantics: for a call, expand to:
- at translate time, construct sorted list of functions that match call
- prefer end-user script highest/first, to provide override capability
- sort others somehow (maybe have explicit ranking like begin(N) probes)
- pseudocode for generated call:
- evaluate PARAMS into temporary variable, for side-effects
- foreach FUNCTION in ALTERNATIVES
- call FUNCTION(PARAM_copies)
- if it returned normally or with an exception/error, done
- else it exited with a 'next' (a new flag in the context structure);
continue looping
- if all alternatives functions exited with 'next', throw an exception
- (All this can be optimized to current code etc, if the translator
detects no 'next' statements in the function body. Ignore
transitively called functions.)
- pseudocode for function-side next: easy peasy
- set function-context nexted-out flag
- return
In this model, any side-effects caused by the alternative functions, before
they run 'next', will persist.
--
You are receiving this mail because:
You are the assignee for the bug.
next reply other threads:[~2015-05-19 15:46 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-19 15:46 fche at redhat dot com [this message]
2015-09-23 21:54 ` [Bug translator/18431] " ajakop at redhat dot com
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bug-18431-6586@http.sourceware.org/bugzilla/ \
--to=sourceware-bugzilla@sourceware.org \
--cc=systemtap@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).