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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - feature request: builtin support for indirect breakpoints"
href="https://bugs.llvm.org/show_bug.cgi?id=47888">47888</a>
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<th>Summary</th>
<td>feature request: builtin support for indirect breakpoints
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<th>Product</th>
<td>lldb
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<th>Version</th>
<td>unspecified
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>lldb-dev@lists.llvm.org
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<th>Reporter</th>
<td>james.widman@gmail.com
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<th>CC</th>
<td>jdevlieghere@apple.com, llvm-bugs@lists.llvm.org
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<pre>Hi all,
Suppose you have two breakpoints, X and Y, and you want Y to be enabled only
after X is hit, and at-most only once for each time X is hit. So you:
- disable Y
- enable X
- add a command to X: 'breakpoint enable Y'
- configure X to auto-continue after running its commands ('-G true')
- add a command to Y: 'breakpoint disable Y'
This works nicely, and you can chain it further so that when you hit breakpoint
b_1, it enables b_2, which enables b_3, ... which enables b_N, and each b_i in
b_2...b_N will disable itself when hit.
But it can get a little unwieldy, especially since there are several steps to
setting up each link in the chain.
So I'm wondering if it would make sense to have a built-in command for this;
maybe like:
breakpoint sequence create b_1 b_2 [... b_N]
... which would arrange for each breakpoint in the sequence, except the last,
to one-shot-enable the next breakpoint in the sequence. It would also have
these effects by default:
1. disable every breakpoint in the sequence except b_1, and
2. set every breakpoint in the sequence, except the last, to auto-continue
... but this could possibly be controlled with options.
I'm not sure whether this is the best way to design the feature; e.g. you might
alternatively want to declare the sequence first and then add new breakpoints
to that sequence (i.e., breakpoints that didn't exist previously).
On the other hand, when I create a bp sequence, here's how that tends to
happen:
0. Initially, I don't know that I want a bp sequence.
1. I create b_N first.
3. Then then I find out that b_N is being hit in contexts that I _don't_
want, and then...
4. I create b_(N-1) and chain it to b_N.
...which seems like an argument in favor of
create-breakpoints-first-and-then-construct-a-sequence-from-existing-breakpoints.
Here are a couple of features I looked for before submitting this request:
- a "one-shot" option to 'breakpoint enable' (so that, if the breakpoint
was disabled before this 'break enable' command, it will go back to being
disabled after it's hit)
- an '--until-breakpoint <breakpoint>' option to 'process continue', which
would one-shot-enable the breakpoint before continuing
Looking forward to feedback!
--James</pre>
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