How to specify new GCC path for CMake

Question

My OS is centos which has a default gcc in path /usr/bin/gcc. But it is old, I need a new version of gcc. So I install a new version in a new path /usr/local/bin/gcc.

But when I run cmake, it still uses the old version gcc path(/usr/bin/gcc) . How can I specify the gcc to new path(/usr/local/bin/gcc).

I have tried to overwrite /usr/bin/gcc with /usr/local/bin/gcc, but it not work.

User · Answer

Set CMAKE C COMPILER to your new path   See here  http   www cmake org Wiki CMake Useful Variables

User · Answer

This question is quite old but still turns up on Google Search. The accepted question wasn't working for me anymore and seems to be aged. The latest information about cmake is written in the cmake FAQ.

There are various ways to change the path of your compiler. One way would be

Set the appropriate CMAKE_FOO_COMPILER variable(s) to a valid compiler name or full path on the command-line using cmake -D. For example:
cmake -G "Your Generator" -D CMAKE_C_COMPILER=gcc-4.2 -D CMAKE_CXX_COMPILER=g++-4.2 path/to/your/source

instead of gcc-4.2 you can write the path/to/your/compiler like this

 cmake -D CMAKE_C_COMPILER=/path/to/gcc/bin/gcc -D CMAKE_CXX_COMPILER=/path/to/gcc/bin/g++ .

User · Answer

This not only works with cmake  but also with   configure and make     configure CC  usr local bin gcc CXX  usr local bin g     Which is resulting in   checking for gcc     usr local bin gcc checking whether the C compiler works    yes

User · Answer

Do not overwrite CMAKE C COMPILER  but export CC  and CXX  before calling cmake   export CC  usr local bin gcc export CXX  usr local bin g   cmake  path to your project make   The export only needs to be done once  the first time you configure the project  then those values will be read from the CMake cache     UPDATE  longer explanation on why not overriding CMAKE C XX  COMPILER after Jake s comment  I recommend against overriding the CMAKE C XX  COMPILER value for two main reasons  because it won t play well with CMake s cache and because it breaks compiler checks and tooling detection   When using the set command  you have three options     without cache  to create a normal variable with cache  to create a cached variable force cache  to always force the cache value when configuring   Let s see what happens for the three possible calls to set   Without cache  set CMAKE C COMPILER  usr bin clang  set CMAKE CXX COMPILER  usr bin clang      When doing this  you create a  normal  variable CMAKE C XX  COMPILER that hides the cache variable of the same name  That means your compiler is now hard-coded in your build script and you cannot give it a custom value  This will be a problem if you have multiple build environments with different compilers  You could just update your script each time you want to use a different compiler  but that removes the value of using CMake in the first place   Ok  then  let s update the cache     With cache  set CMAKE C COMPILER  usr bin clang CACHE PATH     set CMAKE CXX COMPILER  usr bin clang   CACHE PATH       This version will just  not work   The CMAKE C XX  COMPILER variable is already in the cache  so it won t get updated unless you force it   Ah    let s use the force  then     Force cache  set CMAKE C COMPILER  usr bin clang CACHE PATH    FORCE  set CMAKE CXX COMPILER  usr bin clang   CACHE PATH    FORCE    This is almost the same as the  normal  variable version  the only difference is your value will be set in the cache  so users can see it  But any change will be overwritten by the set command   Breaking compiler checks and tooling  Early in the configuration process  CMake performs checks on the compiler  Does it work  Is it able to produce executables  etc  It also uses the compiler to detect related tools  like ar and ranlib  When you override the compiler value in a script  it s  too late   all checks and detections are already done   For instance  on my machine with gcc as default compiler  when using the set command to  usr bin clang  ar is set to  usr bin gcc-ar-7  When using an export before running CMake it is set to  usr lib llvm-3 8 bin llvm-ar

User · Answer

Change CMAKE  lt LANG gt  COMPILER path without triggering a reconfigure  I wanted to compile with an alternate compiler  but also pass -D options on the command-line which would get wiped out by setting a different compiler  This happens because it triggers a re-configure  The trick is to disable the compiler detection with NONE  set the paths with FORCE  then enable language   project  sample project NONE    set  COMPILER BIN  opt compiler bin   set  CMAKE C COMPILER   COMPILER BIN  clang CACHE PATH  clang  FORCE   set  CMAKE CXX COMPILER   COMPILER BIN  clang   CACHE PATH  clang    FORCE    enable language  C CXX     Use a Toolchain file  The more sensible choice is to create a toolchain file   set  CMAKE SYSTEM NAME Darwin    set  COMPILER BIN  opt compiler bin   set  CMAKE C COMPILER   COMPILER BIN  clang CACHE PATH  clang    set  CMAKE CXX COMPILER   COMPILER BIN  clang   CACHE PATH  clang        Then you invoke Cmake with an additional flag  cmake -D CMAKE TOOLCHAIN FILE  path to toolchain file cmake

User · Answer

Export should be specific about which version of GCC/G++ to use, because if user had multiple compiler version, it would not compile successfully.

 export CC=path_of_gcc/gcc-version
 export CXX=path_of_g++/g++-version
 cmake  path_of_project_contain_CMakeList.txt
 make

In case project use C++11 this can be handled by using -std=C++-11 flag in CMakeList.txt

User · Answer

An alternative solution is to configure your project through cmake-gui  starting from a clean build directory  Among the options you have available at the beginning  there s the possibility to choose the exact path to the compilers

[gcc] How to specify new GCC path for CMake

The answer is

Change `CMAKE_<LANG>_COMPILER` path without triggering a reconfigure

Use a Toolchain file

Examples related to gcc

Examples related to cmake

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