[cmake-developers] [CMake 0014727]: libraries list in target_link_libraries() may be optimized

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://www.cmake.org/Bug/view.php?id=14727 
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Reported By:                NAKAMURA Takumi
Assigned To:                
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Project:                    CMake
Issue ID:                   14727
Category:                   CMake
Reproducibility:            always
Severity:                   feature
Priority:                   normal
Status:                     new
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Date Submitted:             2014-02-02 22:57 EST
Last Modified:              2014-02-02 22:57 EST
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Summary:                    libraries list in target_link_libraries() may be
optimized
Description: 
See "suboptimal" cases.

The document says,
"Repeated calls for the same <target> append items in the order called."
I understand they are expected behaviors.

That said, I wish add_executable() (and add_library(MODULE|SHARED)) may have an
option to optimize link order.

FYI, redundant target_link_libraries() for add_library() doesn't cause
suboptimal link order in most cases. See the case in baz.


Consider cases;

  1) To add user-customized target_link_libraries() after a certain macro that
contains add_executable() and its target_link_libraries().

  2) I'd like to write, in target_link_libraries(),
    not "tuned" list of libraries,
    but "actually used in SOURCES" list of libraries.
    I am planning to write "auto dependencies scanner and generator"


FYI, one of my issues is in LLVM.
For example clang/tools/clang-format/CMakeLists.txt
https://github.com/chapuni/clang/blob/master/tools/clang-format/CMakeLists.txt

add_executable(clang-format) emits optimal list of libraries only when;

  target_link_libraries(clang-format clangFormat)

In this case, clanbBasic, clangLex, clangRewriteCore, clangTooling, and
LLVMSupport are *actually referenced* from ClangFormat.cpp.

Steps to Reproduce: 
add_library(foo foo.c)
add_library(bar bar.c)
target_link_libraries(bar foo)
add_library(baz baz.c)
target_link_libraries(baz foo)
target_link_libraries(baz bar)
target_link_libraries(baz foo bar)
add_executable(foobar foobar.c)
if(0)
  # suboptimal -- libfoo.a libbaz.a libbar.a libfoo.a
  target_link_libraries(foobar foo baz)
elseif(0)
  # suboptimal -- libfoo.a libbaz.a libbar.a libfoo.a
  target_link_libraries(foobar foo)
  target_link_libraries(foobar baz)
elseif(0)
  # suboptimal -- libbaz.a libbaz.a libbaz.a libbar.a libfoo.a
  target_link_libraries(foobar baz)
  target_link_libraries(foobar baz baz)
else()
  # optimal -- libbaz.a libbar.a libfoo.a
  target_link_libraries(foobar baz)
endif()
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Issue History 
Date Modified    Username       Field                    Change               
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2014-02-02 22:57 NAKAMURA TakumiNew Issue                                    
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