Fix breakpoint location

Fix breakpoint location

The debugger code erroneously assumed that PC descriptors are
sorted by ascending token_index. That is not the case. This change
fixes the translation from token index to pc descriptor index.
Committed: https://code.google.com/p/dart/source/detail?r=5496

[srdjan, 2012-03-14 22:47:43]

LGTM

http://codereview.chromium.org/9706038/diff/1/runtime/vm/debugger.cc
File runtime/vm/debugger.cc (right):

http://codereview.chromium.org/9706038/diff/1/runtime/vm/debugger.cc#newcode548
runtime/vm/debugger.cc:548: if (desc_token_index < token_index) {
You are searching for closest token after 'token_index', why not for closest
token ? -> abs(desc_token_index - token_index).

You could also stop if best_fit == 0.

[hausner, 2012-03-14 23:10:25]

Thank you!

http://codereview.chromium.org/9706038/diff/1/runtime/vm/debugger.cc
File runtime/vm/debugger.cc (right):

http://codereview.chromium.org/9706038/diff/1/runtime/vm/debugger.cc#newcode548
runtime/vm/debugger.cc:548: if (desc_token_index < token_index) {
On 2012/03/14 22:47:43, srdjan wrote:
> You are searching for closest token after 'token_index', why not for closest
> token ? -> abs(desc_token_index - token_index).
> 
> You could also stop if best_fit == 0.

The token index just before the requested index location is probably on the
previous line, not the one that was requested by the user. 

Yes, I could stop if the match is perfect, but that is almost never going to
happen. The token_index that is passed in represents the first token on a given
source line. That token is probably never a function call. So checking that
additional condition will cost more than it saves.