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IDProjectCategoryView StatusDate SubmittedLast Update
0005999CMakeCMakepublic2007-11-02 17:552016-06-10 14:30
ReporterBrandon Van Every 
Assigned ToBill Hoffman 
PrioritynormalSeveritymajorReproducibilityalways
StatusclosedResolutionmoved 
PlatformOSOS Version
Product Version 
Target VersionFixed in Version 
Summary0005999: REGEX ^ does not anchor against the original string
Description^ doesn't anchor against the original input string. It anchors against the string as it is processed! If replacements cause the string to have a new beginning, it anchors against the new beginning. Perl does not exhibit this behavior. I know CMake is not Perl, but Perl is a good baseline for "sanity" in regex processing. If a ^ anchor isn't respected then it renders the use of such an anchor fairly pointless.

Reproducer script anchor.cmake:

SET(sillystring "I wanna rock!")
MESSAGE("original string:")
MESSAGE("${sillystring}")
MESSAGE("expecting replacement to remove the leading 'I'. Instead we get:")
STRING(REGEX REPLACE
  "^."
  ""
  out "${sillystring}")
MESSAGE("${out}")


C:\devel\src\cbugs\anchor>cmake -P anchor.cmake
original string:
I wanna rock!
expecting replacement to remove the leading 'I'. Instead we get:


C:\devel\src\cbugs\anchor>


For comparison, a Perl script anchor.pl:

my $sillystring;
$sillystring = "I wanna rock!\n";
print "Original string:\n";
print $sillystring;
print "Expecting replacement to remove the leading 'I'. In Perl we get:\n";
$sillystring =~ s/^.//;
print $sillystring;


bvanevery@OLDFAITHFUL /c/devel/moz
$ perl anchor.pl
Original string:
I wanna rock!
Expecting replacement to remove the leading 'I'. In Perl we get:
 wanna rock!

bvanevery@OLDFAITHFUL /c/devel/moz
$
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  Notes
(0009626)
Brandon Van Every (reporter)
2007-11-03 16:27

 Additionally, a regex of ".$" only replaces 1 character at the end of the string. CMake's behavior is inconsistent with respect to leading and trailing anchors, proving that this is a bug and not something CMake does "on principle" out of greed.

SET(sillystring "I wanna rock!")
MESSAGE("original string:")
MESSAGE("${sillystring}")
MESSAGE("expecting replacement to remove the leading 'I'. Instead we get:")
STRING(REGEX REPLACE
  "^."
  ""
  out "${sillystring}")
MESSAGE("${out}")
MESSAGE("$ doesn't have the problem, only ^")
MESSAGE("Here we get rid of the trailing '!'")
STRING(REGEX REPLACE
  ".$"
  ""
  out "${sillystring}")
MESSAGE("${out}")

C:\devel\src\cbugs\anchor>cmake -P anchor.cmake
original string:
I wanna rock!
expecting replacement to remove the leading 'I'. Instead we get:

$ doesn't have the problem, only ^
Here we get rid of the trailing '!'
I wanna rock

C:\devel\src\cbugs\anchor>
(0041401)
Kitware Robot (administrator)
2016-06-10 14:27

 Resolving issue as `moved`.

This issue tracker is no longer used. Further discussion of this issue may take place in the current CMake Issues page linked in the banner at the top of this page.

 Issue History
Date Modified Username Field Change
2007-11-02 17:55 Brandon Van Every New Issue
2007-11-02 17:59 Brandon Van Every Description Updated
2007-11-03 16:27 Brandon Van Every Note Added: 0009626
2007-12-14 20:49 Bill Hoffman Status new => assigned
2007-12-14 20:49 Bill Hoffman Assigned To => Bill Hoffman
2016-06-10 14:27 Kitware Robot Note Added: 0041401
2016-06-10 14:27 Kitware Robot Status assigned => resolved
2016-06-10 14:27 Kitware Robot Resolution open => moved
2016-06-10 14:30 Kitware Robot Status resolved => closed

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