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Do not always propagate linker language preference

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The commit "Consider link dependencies for link language" taught CMake
to propagate linker language preference from languages compiled into
libraries linked by a target.  It turns out this should only be done for
some languages, such as C++, because normally the language of the
program entry point (main) should be used.

We introduce variable CMAKE_<LANG>_LINKER_PREFERENCE_PROPAGATES to tell
CMake whether a language should propagate its linker preference across
targets.  Currently it is true only for C++.
This commit is contained in:
Brad King 2009-07-30 10:59:37 -04:00
parent fd633b33cf
commit fcab87c9f8
3 changed files with 40 additions and 15 deletions
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1
Modules/CMakeCXXCompiler.cmake.in
View File

@ -22,6 +22,7 @@ SET(CMAKE_CXX_COMPILER_ID_RUN 1)
SET(CMAKE_CXX_IGNORE_EXTENSIONS inl;h;H;o;O;obj;OBJ;def;DEF;rc;RC)
SET(CMAKE_CXX_SOURCE_FILE_EXTENSIONS C;M;c++;cc;cpp;cxx;m;mm)
SET(CMAKE_CXX_LINKER_PREFERENCE 30)
SET(CMAKE_CXX_LINKER_PREFERENCE_PROPAGATES 1)
# Save compiler ABI information.
SET(CMAKE_CXX_SIZEOF_DATA_PTR "@CMAKE_CXX_SIZEOF_DATA_PTR@")

21
Source/cmDocumentVariables.cxx
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@ -1201,12 +1201,25 @@ void cmDocumentVariables::DefineVariables(cmake* cm)
"language and reports the results in this variable.", false,
"Variables for Languages");
cm->DefineProperty
("CMAKE_<LANG>_LINKER_PREFERENCE_PROPAGATES", cmProperty::VARIABLE,
"True if CMAKE_<LANG>_LINKER_PREFERENCE propagates across targets.",
"This is used when CMake selects a linker language for a target. "
"Languages compiled directly into the target are always considered. "
"A language compiled into static libraries linked by the target is "
"considered if this variable is true.", false,
"Variables for Languages");
cm->DefineProperty
("CMAKE_<LANG>_LINKER_PREFERENCE", cmProperty::VARIABLE,
"Determine if a language should be used for linking.",
"If this is \"Preferred\" then if there is a mixed "
"language shared library or executable, then this "
"languages linker command will be used.",false,
"Preference value for linker language selection.",
"The \"linker language\" for executable, shared library, and module "
"targets is the language whose compiler will invoke the linker. "
"The LINKER_LANGUAGE target property sets the language explicitly. "
"Otherwise, the linker language is that whose linker preference value "
"is highest among languages compiled and linked into the target. "
"See also the CMAKE_<LANG>_LINKER_PREFERENCE_PROPAGATES variable.",
false,
"Variables for Languages");
cm->DefineProperty

33
Source/cmTarget.cxx
View File

@ -441,18 +441,15 @@ void cmTarget::DefineProperties(cmake *cm)
cm->DefineProperty
("LINKER_LANGUAGE", cmProperty::TARGET,
"Specifies language whose link tool should be used (obselete).",
"Specifies language whose compiler will invoke the linker.",
"For executables, shared libraries, and modules, this sets the "
"language whose link tool is used to link the target "
"language whose compiler is used to link the target "
"(such as \"C\" or \"CXX\"). "
"CMake 2.6 and below select a linker language automatically "
"based on the languages compiled into the target. "
"This property overrides the default in case one of the "
"linked libraries uses another language. "
"A typical example is a C executable linking to a static archive "
"containing C++ object files. "
"CMake 2.8 and above account for languages in linked targets "
"automatically, making this property unnecessary.");
"A typical value for an executable is the language of the source "
"file providing the program entry point (main). "
"If not set, the language with the highest linker preference "
"value is the default. "
"See documentation of CMAKE_<LANG>_LINKER_PREFERENCE variables.");
cm->DefineProperty
("LOCATION", cmProperty::TARGET,
@ -2506,11 +2503,25 @@ void cmTarget::ComputeLinkClosure(const char* config, LinkClosure& lc)
{
// Find the language with the highest preference value.
cmTargetSelectLinker tsl(this);
// First select from the languages compiled directly in this target.
for(std::vector<std::string>::const_iterator li = impl->Languages.begin();
li != impl->Languages.end(); ++li)
{
tsl.Consider(li->c_str());
}
// Now consider languages that propagate from linked targets.
for(std::set<cmStdString>::const_iterator sit = languages.begin();
sit != languages.end(); ++sit)
{
tsl.Consider(sit->c_str());
std::string propagates = "CMAKE_"+*sit+"_LINKER_PREFERENCE_PROPAGATES";
if(this->Makefile->IsOn(propagates.c_str()))
{
tsl.Consider(sit->c_str());
}
}
lc.LinkerLanguage = tsl.Choose();
}
}