[LLVMdev] CMake: Gold linker detection

[Sumanth Gundapaneni]

I reacted as per my case.  You need CFLAGS in order to what linker you might be using.

In case of clang, you can use “-fuse-ld” to control the invocation of linker.

In my opinion, it is not necessary to carry forward LDFLAGS unless you want to control specific parts of the linker.

 

In my case, I have a cross compiler for ARM and I usually compile the code with

Clang –sysroot=<path_to_sysroot> --gcc-toolchain=<path_to_toolchain> -target=<triple> file.c 

Where I pass “–sysroot=<path_to_sysroot> --gcc-toolchain=<path_to_toolchain> -target=<triple>” as CMAKE_C_FLAGS :)

With out –gcc-toolchain, clang cannot find the linker and picks the system linker which is usually /usr/bin/ld on a linux system.

 

 

--Sumanth G

From: C Bergström [mailto:cbergstrom at pathscale.com] 
Sent: Tuesday, January 27, 2015 11:51 AM
To: Sumanth Gundapaneni
Cc: llvmdev at cs.uiuc.edu; Rafael Ávila de Espíndola; Takumi NAKAMURA
Subject: Re: [LLVMdev] CMake: Gold linker detection

 

 

 

On Wed, Jan 28, 2015 at 2:27 AM, Sumanth Gundapaneni <sgundapa at codeaurora.org <mailto:sgundapa at codeaurora.org> > wrote:

Hi Rafael,

                  I looked at the code which you pushed a while ago to check for the gold linker.

Code below:

execute_process(

    COMMAND ${CMAKE_C_COMPILER} -Wl,--version

    OUTPUT_VARIABLE stdout 

    ERROR_QUIET)

  if("${stdout}" MATCHES "GNU gold")

    set(LLVM_LINKER_IS_GOLD ON)

  endif()

 

 

I was trying to build runtime libraries (compiler-rt) for ARM using “clang” which includes this code.

A while ago, I saw the error message until geek4civic fixed it with “ERROR_QUIET”.

I usually specify my sysroot and tool chain(linker) through CFLAGS. 

To fortify the logic, “${CMAKE_C_COMPILER} ${CMAKE_C_FLAGS}  -Wl, --version” would be ideal than “${CMAKE_C_COMPILER}  -Wl, --version” which works mostly for gnu compilers.

Let me know, I can push a patch 

 

execute_process(

-      COMMAND ${CMAKE_C_COMPILER} -Wl,--version

+    COMMAND “${CMAKE_C_COMPILER}  ${CMAKE_C_FLAGS}” -Wl,--version

    OUTPUT_VARIABLE stdout 

    ERROR_QUIET)

  if("${stdout}" MATCHES "GNU gold")

    set(LLVM_LINKER_IS_GOLD ON)

  endif()

 

While this may be convenient I don't think it's strictly correct.

 

CFLAGS != LDFLAGS

 

I think if extra flags are going to be passed it should be LD specific since that's what this is intended to check.

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