Op 22-03-18 om 20:28 schreef Harald van Dijk:
> On 22/03/2018 03:40, Martijn Dekker wrote:
>> evalvar() records empty expansion results (varlen == 0) as string
>> regions that need to be scanned for IFS characters. This is pointless,
>> because there is nothing to split.
>
> varlen may be set to -1 when an unset variable is expanded. If it's
> beneficial to avoid recording empty regions to scan for IFS characters,
> should those also be excluded?
Agreed. Updated patch attached.
>> This patch fixes the bug that, given no positional parameters, unquoted
>> $@ and $* incorrectly generate one empty field (they should generate no
>> fields). Apparently that was a side effect of the above.
>
> This seems weird though. If you want to remove the recording of empty
> regions because they are pointless, then how does removing them fix a
> bug? Doesn't this show that empty regions do have an effect? Perhaps
> they're not supposed to have any effect, perhaps it's a specific
> combination of empty regions and something else that triggers some bug,
> and perhaps that combination can no longer occur with your patch.
The latter is my guess, but I haven't had time to investigate it.
I *did* investigate whether the patch introduces other bugs, and haven't
found any new ones.
I successfully ran this large IFS and PPs test script from AT&T against
dash with this patch:
http://web.archive.org/web/20050414022354/http://www.research.att.com/~gsf/public/ifs.sh
My own modernish regression test suite, which tests some pretty crazy
things including lots of IFS and positional parameters stuff, also
passes completely:
git clone https://github.com/modernish/modernish
cd modernish
dash bin/modernish --test
(still under development, may occasionally break)
- M.
diff --git a/src/expand.c b/src/expand.c
index 705fef7..c3d20a4 100644
--- a/src/expand.c
+++ b/src/expand.c
@@ -771,7 +771,7 @@ vsplus:
if (subtype == VSNORMAL) {
record:
- if (!easy)
+ if (!easy || varlen <= 0)
goto end;
recordregion(startloc, expdest - (char *)stackblock(), quoted);
goto end;
