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| ID | Project | Category | View Status | Date Submitted | Last Update | ||||
| 0014737 | CMake | CMake | public | 2014-02-05 10:49 | 2016-06-10 14:31 | ||||
| Reporter | Alex Merry | ||||||||
| Assigned To | Kitware Robot | ||||||||
| Priority | normal | Severity | feature | Reproducibility | always | ||||
| Status | closed | Resolution | moved | ||||||
| Platform | GNU | OS | Linux | OS Version | |||||
| Product Version | CMake-2-8 | ||||||||
| Target Version | Fixed in Version | ||||||||
| Summary | 0014737: if(ENV{FOO}) should work like if(FOO) but for env vars | ||||||||
| Description | A script like if($ENV{FOO}) # do something endif() will never evaluate the statements in the if() branch, regardless of the value of the environment variable FOO. | ||||||||
| Steps To Reproduce | Store the attached testenv.cmake somewhere, then run FOO="" cmake -P testenv.cmake As expected, the output is -- $ENV{FOO} = -- $ENV{FOO} evaluates to FALSE -- ENV{FOO} evaluates to FALSE Now try FOO="bar" cmake -P testenv.cmake The output is -- $ENV{FOO} = bar -- $ENV{FOO} evaluates to FALSE -- ENV{FOO} evaluates to FALSE when the expected output would be -- $ENV{FOO} = bar -- $ENV{FOO} evaluates to TRUE -- ENV{FOO} evaluates to TRUE | ||||||||
| Additional Information | Tested with cmake 2.8.12 and cmake 2.8.12.20140204-g5414b | ||||||||
| Tags | No tags attached. | ||||||||
| Attached Files |  testenv.cmake [^] (303 bytes) 2014-02-05 10:49 | ||||||||
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| Notes | |
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(0035040) Brad King (manager) 2014-02-05 12:39 |
The if command documentation: http://www.cmake.org/cmake/help/v2.8.12/cmake.html#command:if [^] explains that the value it is given is first checked against a boolean constant and then treated as a variable name. Since you're evaluating "$ENV{FOO}" the CMake language expands the value of the environment variable before the if() command ever sees the reference. Therefore for value "bar" the if() command sees if(bar) Since "bar" is not a boolean constant then if() looks for a variable called "bar" and since that is not defined the result is false. Using FOO=1 results in evaluation to true. Prior to policy CMP0012, introduced in CMake 2.8.0, if() would consider variables before named constants like "TRUE" so one must add cmake_minimum_required(VERSION 2.8) to ensure modern behavior. A common idiom for this use case is: set(FOO "$ENV{FOO}") if(FOO) ... endif() |
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(0035041) Brad King (manager) 2014-02-05 12:41 |
One may also use if(DEFINED ENV{FOO}) endif() to detect whether the environment variable is defined at all. |
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(0035042) Alex Merry (reporter) 2014-02-05 12:45 |
Maybe I shouldn't have used that particular construction in the title of the bug. What surprised me was that if(ENV{FOO}) also did not work. |
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(0035043) Alex Merry (reporter) 2014-02-06 07:29 |
I'm happy for this to be considered a feature request, rather than a bug, BTW: it would be really convenient for if(ENV{DESTDIR}) # modify installation command endif() to work (in the context of install(CODE), of course). |
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(0035044) Brad King (manager) 2014-02-06 08:52 |
The proper place in the code to make this work is at the bottom of GetBooleanValue in cmIfCommand.cxx: http://cmake.org/gitweb?p=cmake.git;a=blob;f=Source/cmIfCommand.cxx;hb=v2.8.12.2#l263 [^] That's where it falls back to looking for a variable definition. One could teach that step to recognize ENV{} syntax and check the environment value instead. |
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(0042477) Kitware Robot (administrator) 2016-06-10 14:29 |
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. |
| Notes |
| Issue History | |||
| Date Modified | Username | Field | Change |
| 2014-02-05 10:49 | Alex Merry | New Issue | |
| 2014-02-05 10:49 | Alex Merry | File Added: testenv.cmake | |
| 2014-02-05 12:39 | Brad King | Note Added: 0035040 | |
| 2014-02-05 12:41 | Brad King | Note Added: 0035041 | |
| 2014-02-05 12:45 | Alex Merry | Note Added: 0035042 | |
| 2014-02-06 07:29 | Alex Merry | Note Added: 0035043 | |
| 2014-02-06 08:52 | Brad King | Note Added: 0035044 | |
| 2014-02-06 08:52 | Brad King | Severity | minor => feature |
| 2014-02-06 08:52 | Brad King | Status | new => backlog |
| 2014-02-06 08:52 | Brad King | Summary | $ENV{FOO} always evaluates to FALSE => if(ENV{FOO}) should work like if(FOO) but for env vars |
| 2016-06-10 14:29 | Kitware Robot | Note Added: 0042477 | |
| 2016-06-10 14:29 | Kitware Robot | Status | backlog => resolved |
| 2016-06-10 14:29 | Kitware Robot | Resolution | open => moved |
| 2016-06-10 14:29 | Kitware Robot | Assigned To | => Kitware Robot |
| 2016-06-10 14:31 | Kitware Robot | Status | resolved => closed |
| Issue History |
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