[CMake] CMAKE_EXE_LINKER_FLAGS for shared libraries?
Michael Hertling
mhertling at online.de
Fri Dec 16 05:28:52 EST 2011
On 12/13/2011 11:19 PM, Michael Hertling wrote:
> On 12/13/2011 09:21 PM, David Cole wrote:
>> On Tue, Dec 13, 2011 at 2:09 PM, Robert Dailey <rcdailey at gmail.com> wrote:
>>> Thanks for the info. It's a bit disappointing that it doesn't work like I
>>> expect. The CMAKE_MFC_FLAG should work as you say the link flags should, but
>>> it does not. As long as CMAKE_MFC_FLAG is set before I create my target, it
>>> works. Since CMAKE_SHARED_LINK_FLAGS does not work the same, I consider this
>>> a bug. There is no reason for it to exist up to the end of the file... it
>>> should only exist up to the call to create the target. For example, if I
>>> want to have 2 calls to add_library() in the same file, but specify link
>>> flags differently for each, how am I expected to do this without using the
>>> target specific property?
>>
>> You're not expected to do that. You should use the target property in
>> that case. That's what they're there for.
>>
>> Or use sub-directory organization to have one target per sub-dir, and
>> then set the variable appropriately in each sub-dir's CMakeLists file.
>>
>> And, there is a reason for it to exist up to the end of the file: it's
>> called backwards compatibility, and we take it pretty seriously.
>>
>> The fact is that some variables are examined at configure-time, while
>> CMake is processing add_executable and add_library calls, and all the
>> other myriad commands that are affected by variables values, ...
>>
>> ... and some variables are examined later at generate-time, *after*
>> CMake is done processing the commands, (in other words, "at the end of
>> the file").
>>
>> So: this particular case may be considered a bug by some, and a
>> feature by others. Personally, I'm not sure what side of that fence to
>> fall on.
>>
>> However, the primary purpose of this mailing list is to try to show
>> you how you can do what you want to do with *existing* CMake. We also
>> like to discuss options and future plans here.
>>
>> If you would like to report this as a bug, please feel free to add a
>> bug report to the bug tracker.
>
> As for me, I wouldn't consider it as a bug, but it should perhaps be
> mentioned in the documentation which variables undergo this kind of
> lazy evaluation, i.e. configure-time vs. generate-time evaluation.
>
> "This variable is not evaluated until the generation takes place,
> so the value at the end of the CMakeLists.txt will be in effect."
Alternatively, one might add a brief description of the two evaluation
kinds right beneath [1] but before [2] and mark the generation-time-
evaluated variables with a short tag afterwards.
Regards,
Michael
> [1] http://www.cmake.org/cmake/help/cmake-2-8-docs.html#section_Variables
> [2] http://www.cmake.org/cmake/help/cmake-2-8-docs.html#section_VariablesThatChangeBehavior
>>> On Mon, Dec 12, 2011 at 11:26 PM, Michael Wild <themiwi at gmail.com> wrote:
>>>>
>>>> It needs to exist **at the end** of the CMakeLists.txt file containing
>>>> the target. If you don't want to do that (or can't, as in your case),
>>>> you can use the LINK_FLAGS target property instead.
>>>>
>>>> HTH
>>>>
>>>> Michael
>>>>
>>>> On 12/12/2011 11:39 PM, Robert Dailey wrote:
>>>>> I have attached a small CMake project that reproduces the issue I'm
>>>>> referring to. Please take a look :)
>>>>>
>>>>> ---------
>>>>> Robert Dailey
>>>>>
>>>>>
>>>>> On Mon, Dec 12, 2011 at 4:11 PM, Robert Dailey <rcdailey at gmail.com
>>>>> <mailto:rcdailey at gmail.com>> wrote:
>>>>>
>>>>> I forgot to say that the main issue is that my /NODEFAULTLIB link
>>>>> flag isn't showing up in visual studio.
>>>>>
>>>>> ---------
>>>>> Robert Dailey
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Dec 12, 2011 at 4:10 PM, Robert Dailey <rcdailey at gmail.com
>>>>> <mailto:rcdailey at gmail.com>> wrote:
>>>>>
>>>>> Another issue...
>>>>>
>>>>> At what point is it most important for the values of
>>>>> CMAKE_SHARED_LINK_FLAGS to exist? I set the value of this
>>>>> variable before my call to add_library(), however after that at
>>>>> some point the flags will get reverted because I'm stepping out
>>>>> of function scope. Does it need to exist up to the end of the
>>>>> current cmake script? My flow is basically this (pseudo call
>>>>> stack):
>>>>>
>>>>> Enter CMakeLists.txt
>>>>> - Call define_project() function (in a separate cmake module)
>>>>> - - Call ignore_libs() function
>>>>> - - - Set CMAKE_SHARED_LINK_FLAGS with PARENT_SCOPE
>>>>> - - Call create_target() function
>>>>> - - - Call add_library() command
>>>>> Leave CMakeLists.txt
>>>>>
>>>>> I've done some testing and I find that before the call to
>>>>> add_library(), my flags are setup properly in the
>>>>> CMAKE_SHARED_LINK_FLAGS variable.
>>>>>
>>>>> ---------
>>>>> Robert Dailey
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Dec 12, 2011 at 2:20 PM, Michael Wild <themiwi at gmail.com
>>>>> <mailto:themiwi at gmail.com>> wrote:
>>>>>
>>>>> On 12/12/2011 09:13 PM, Robert Dailey wrote:
>>>>> > On Mon, Dec 12, 2011 at 2:10 PM, David Cole
>>>>> <david.cole at kitware.com <mailto:david.cole at kitware.com>
>>>>> > <mailto:david.cole at kitware.com
>>>>> <mailto:david.cole at kitware.com>>> wrote:
>>>>> >
>>>>> > Apparently, they are undocumented, but there are also:
>>>>> >
>>>>> > CMAKE_SHARED_LINKER_FLAGS and
>>>>> CMAKE_MODULE_LINKER_FLAGS (and their
>>>>> > per-config variants) for SHARED and MODULE library
>>>>> targets as well.
>>>>> >
>>>>> > Use CMAKE_SHARED_LINKER_FLAGS instead.
>>>>> >
>>>>> >
>>>>> > Thanks for the information guys. I'm having a minor
>>>>> problem with these
>>>>> > variables though.
>>>>> >
>>>>> > Here is how I use it:
>>>>> >
>>>>> > set( CMAKE_SHARED_LINKER_FLAGS
>>>>> ${CMAKE_SHARED_LINKER_FLAGS}
>>>>> > /NODEFAULTLIB:\"${lib}\" )
>>>>> >
>>>>> > Prior to calling the set above, the shared linker flags
>>>>> look like this:
>>>>> >
>>>>> > /STACK:10000000 /machine:X86
>>>>> >
>>>>> > After calling the set above, it looks like this:
>>>>> >
>>>>> > /STACK:10000000 /machine:X86 ;/NODEFAULTLIB:"LIBC"
>>>>> >
>>>>> > For some reason a semi-colon is being inserted prior to
>>>>> the
>>>>> > /NODEFAULTLIB part. I don't know why this is happening but
>>>>> visual studio
>>>>> > is complaining about it. Any reason why this is happening?
>>>>> Thanks.
>>>>> >
>>>>>
>>>>> That's how CMake works.
>>>>>
>>>>> set(VAR val1 val2 val3)
>>>>>
>>>>> defines a *list* where the elements are separated by a
>>>>> semi-colon (;).
>>>>> To prevent that, quote the assignment:
>>>>>
>>>>> set(VAR "val1 val2 val3")
>>>>>
>>>>>
>>>>> Michael
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