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0014619

CMake

public

2013-12-03 02:43

2014-06-02 08:37

Reporter

nOOb3167

Assigned To

Priority

normal

Severity

major

Reproducibility

always

Status

closed

Resolution

won't fix

Platform

Windows

OS Version

Product Version

CMake 2.8.12

Target Version

Fixed in Version

Summary

0014619: Windows: Regression affecting CMAKE_FIND_ROOT_PATH interaction with FIND_* commands, introduced since 2.8.11

Description

Due to an unrelated fix of issue 0010994, commit f9eee7f1, regarding drive letter paths on Windows, CMAKE_FIND_ROOT_PATH scenarios break on Windows hosts.

The correct operation of find_file and other find_* command calls in CMAKE_FIND_ROOT_PATH scenarios on Windows might be possible to restore, while
still keeping the rest of the issue 0010994 fix.

Steps To Reproduce

Unpack uploaded test example.

= Contents =
CMakeLists.txt : CMakeLists file to be used.
testToolChain.toolchain : Toolchain file demonstrating a workaround.
root/ : Directory to be used as CMAKE_FIND_ROOT_PATH.
root/include/dummyFile.txt : File to be searched for by FIND_FILE.
Build/ : Out-of-source build directory.
                             Used to get a clean state between the multiple
                             cmake invocations that will be performed.
= Reproducing =
The CMakeLists.txt will be Configured by CMake versions 2.8.11 and 2.8.12.
The results will differ.

== Steps ==

=== 2.8.11 ===
1. Use CMake version 2.8.11
2. Invoke from Build/ :
    cmake ..

The variable TEST_NOROOT is set to path of dummyFile.txt.

=== 2.8.12 ===
1. Use CMake version 2.8.12
2. Invoke from Build/ :
    cmake ..

The variable TEST_NOROOT is not set to path of dummyFile.txt - Its value is TEST_NOROOT-NOTFOUND.
This result differs from 2.8.11 and is therefore a regression.

Additional Information

Observing the changelog (http://www.cmake.org/Wiki/CMake/ChangeLog [^]), shows the following line in the 'Changes in CMake 2.8.12-rc1 (since 2.8.11.2)' entry:
"Windows: Search '/' prefix only when cross compiling (0010994)"

A developer comment on issue 0010994 (http://www.cmake.org/Bug/view.php?id=10994#c32940 [^]), links to the attempted fix commit f9eee7f1 (http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=f9eee7f1 [^]).

According to the f9eee7f1 commit message:
"Fix WindowsPaths.cmake to add '/' to CMAKE_SYSTEM_PREFIX_PATH only when
cross-compiling to Windows from a non-Windows host."
The root ('/') path is made to be omitted from CMAKE_SYSTEM_PREFIX_PATH on Windows hosts, as a change from 2.8.11 to 2.8.12.

I claim this omission breaks CMAKE_FIND_ROOT_PATH on Windows hosts.
As demonstrated by the uploaded test example, a command call of the form:
"find_file(<VAR> NAMES <NAMES> PATH_SUFFIXES <SUFFIXES>)"
Will no longer function in presence of CMAKE_FIND_ROOT_PATH.

As many Find* Modules included with CMake use find_file command calls of the above form, these Modules therefore become unable to function in a CMAKE_FIND_ROOT_PATH scenario.

The uploaded test example also contains a toolchain file.
The toolchain file appends '/' to CMAKE_SYSTEM_PREFIX_PATH.
The addition of '/' allows the command call to succeed.
This indicates the ab-or-pre-sence of '/' has a breaking effect on find_file.

The uploaded test example also attempts a command call of the form:
"find_file(<VAR> NAMES <NAMES> PATHS / PATH_SUFFIXES <SUFFIXES>)"
Here a 'PATHS /' parameter is added with respect to the previous failing call.
The addition of '/' in PATHS also allows the command call to succeed.

Commit f9eee7f1, already mentioned and linked in a section above,
describes the reason for '/' omission as:
"This will avoid searching and finding local paths without a drive letter on Windows."

In a CMAKE_FIND_ROOT_PATH scenario with CMAKE_SYSTEM_PREFIX_PATH containing '/', a drive-less path will never be formed by find_file. The operation of find_file, relevant to this scenario, is described next.

Assuming values of:
CMAKE_FIND_ROOT_PATH = F:\root
CMAKE_SYSTEM_PREFIX_PATH = '/' # (Or just containing '/' among other items)
A find_file command call will prefix F:\root to '/', getting 'F:\root\'.
This path will then be considered for the search.
(The find_file command documentation (http://www.cmake.org/cmake/help/v2.8.12/cmake.html [^]), describes CMAKE_SYSTEM_PREFIX_PATH as used during the '5.' step of the search process. The search path prefixing effect of CMAKE_FIND_ROOT_PATH is described towards the end of find_file documentation.)

Using find_file in a CMAKE_FIND_ROOT_PATH scenario, the 'paths without a drive letter' issue does not occur, as '/' is used just to form a longer path by concatenation of CMAKE_FIND_ROOT_PATH with CMAKE_SYSTEM_PREFIX_PATH.

Commit f9eee7f1 has therefore introduced a new bug (A regression), while attempting to fix an unrelated case.

Notes
(0034689) Brad King (manager) 2013-12-03 08:51	The CMAKE_FIND_ROOT_PATH is not a list of locations to search and was only made to appear to be so by '/' in the CMAKE_SYSTEM_PREFIX_PATH. See explanation in 0014591. Use CMAKE_PREFIX_PATH instead to add your own prefixes.

(0036050) Robert Maynard (manager) 2014-06-02 08:37	Closing resolved issues that have not been updated in more than 4 months.

Issue History
Date Modified	Username	Field	Change
2013-12-03 02:43	nOOb3167	New Issue
2013-12-03 02:43	nOOb3167	File Added: DummyProj.zip
2013-12-03 08:49	Brad King	Relationship added	duplicate of 0014591
2013-12-03 08:51	Brad King	Note Added: 0034689
2013-12-03 08:51	Brad King	Status	new => resolved
2013-12-03 08:51	Brad King	Resolution	open => won't fix
2014-06-02 08:37	Robert Maynard	Note Added: 0036050
2014-06-02 08:37	Robert Maynard	Status	resolved => closed