Document these variables.
Change our convention for setting these variables from:
set(CMAKE_EXE_LINKER_FLAGS_INIT "...")
to
string(APPEND CMAKE_EXE_LINKER_FLAGS_INIT " ...")
so that any value previously set by a toolchain file will be used.
The CMAKE_SHARED_LIBRARY_LINK_<LANG>_FLAGS setting has always been meant
for flags needed to export symbols from executables for use by shared
library plugins. Since commit v3.4.0-rc1~58^2~1 (CMP0065: Restrict the
use of CMAKE_SHARED_LIBRARY_LINK_<LANG>_FLAGS, 2015-08-24) this is made
explicit by using the flags only for executables with ENABLE_EXPORTS,
guarded by CMP0065 for compatibility.
On some platforms we were accidentally using this setting to pass other
flags to the linker:
* AIX: -bnoipath, -brtl
* HP-UX: +s, +nodefaultrpath
These flags are incorrectly dropped when CMP0065 is set to NEW. Fix
this by moving the flags to more appropriate places for linking
executables.
The flag was added incorrectly by commit 9c3a6eb4 (Need -brtl when creating
shared libraries, 2003-05-16). According to "man ld" the -G option implies
"-brtl -bnortllib ...", -brtl implies "-brtllib", and -brtllib should only be
used for executables, not shared libraries. Therefore it is incorrect and
unnecessary to specify -brtl explicitly after -G.
Reported-by: Kevin Burge <kcburge@gmail.com>
The GNU compiler front-ends on AIX invoke the linker with flags of the
form "-L/path/to/gnu/runtime/lib" to tell ld where to find the language
runtime libraries. They depend on the default libpath behavior
documented in "man ld" to add the -L paths also to the runtime libpath
so the dynamic loader can find the language runtime libraries. This
differs from platforms whose linkers have distinct -rpath flags that
non-system compilers can use to tell the dynamic loader where to find
their language runtime libraries.
Since commit 96fd5909 (Implement linking with paths to library files,
2008-01-22) CMake always passes "-Wl,-blibpath:" followed by any
project-defined RPATH plus "/usr/lib:/lib" in order to explicitly set
the runtime libpath and avoid getting all the project -L paths in the
runtime libpath. The explicit libpath prevents the GNU compiler runtime
library -L paths from being placed in the libpath and then the dynamic
loader fails to find the language runtime libraries.
CMake already detects the implicit link directories for each language
since commit 07ea19ad (Implicit link info for C, CXX, and Fortran,
2009-07-23). Add the implicit link directories to the explicit runtime
libpath for GNU compilers on AIX to fix this use case.
Move RPATH flags out of Platform/AIX.cmake into platform-specific
compiler information files Platform/AIX-XL and Platform/AIX-GNU.
The flags need to be set for each compiler of each language.
This moves GNU compiler flags into new-style modules
Compiler/GNU-<lang>.cmake
Platform/<os>-GNU-<lang>.cmake
We use language-independent helper modules
Compiler/GNU.cmake
Platform/<os>-GNU.cmake
to define macros consolidating the information.
Brad King
Marc Chevrier
Todd Gamblin