problems with step debugging

[John Rose]

On Feb 4, 2014, at 4:21 AM, Jochen Theodorou <blackdrag at gmx.org> wrote:

> If I know how it is supposed to look like, I can change our compiler to 
> emit the line number information exactly where suggested and then see if 
> it works. But for that I missing that information :(

Here is the information I know about, which is very little, from the JVMS:

> 4.7.12 The LineNumberTable Attribute
> 
> The LineNumberTable attribute is an optional variable-length attribute in the attributes table of a Code (§4.7.3) attribute. It may be used by debuggers to determine which part of the Java Virtual Machine code array corresponds to a given line number in the original source file.

"It may be used by debuggers"... which implies on the other hand "it may not".

It could be that javac emits "something reasonable" for line numbers and IDEs and debuggers do "something reasonable" with it, and nobody can say what's wrong if the handshake fails.

If this is how it works, it's OK as long as only a few people are involved in the handshake.  Perhaps somebody in the know needs to write a little blog entry or wiki page on how line numbering works.

— John
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