Setting up an environment for a Binary snapshot of gcc

[Andrew C Aitchison]

On Thu, 22 Jan 2026, Ian Bruntlett wrote:
> Hi,
> 
> I have 2 questions about Ubuntu system administration:
> 
> *The situation.*
> Using Ubuntu 24.04.3 x86_64 LTS
> I installed gcc-latest_16.0.0-20260111git8e4107a1b3d4.deb
> $ sudo dpkg --install gcc-latest_16.0.0-20260111git8e4107a1b3d4.deb
> The .deb file came from https://jwakely.github.io/pkg-gcc-latest/
> 
> This prerelease of gcc runs from /opt/gcc-latest/bin so, to get that onto
> the PATH, I put these 2 lines at the bottom of .bashrc:
> # Things for running gcc-latest
> PATH=/opt/gcc-latest/bin:$PATH
> 
> *Question 1.*
> Is that sensible? With a bit more work I got g++ to compile a simple Hello
> World programme - I needed to sudo apt install binutils first.
> 
> So that Hello World could find the standard C++ library, I had to source a
> shell script which did this:
> #!/bin/bash
> echo $PATH
> set -x
> export LD_LIBRARY_PATH=/opt/gcc-latest/lib64
> 
> *Question 2.*
> Is that sensible? Should I put it in .bashrc as well?

.bashrc is one way to do it, but I suggest that you
explore the "environment-modules" package.

For a differently packaged/installed version of gcc 16 I have
this module file:

#%Module########################################

## conflict gcc
conflict llvm

set gnu_basedir  /usr/lib/gcc-snapshot
set GNU_BIN $gnu_basedir/bin
setenv CC      gcc-snapshot
setenv CXX     g++-snapshot
setenv GNU_PATH $GNU_BIN
prepend-path   PATH     $gnu_basedir/bin
prepend-path   CPATH    $gnu_basedir/include/c++
setenv LD_SHARED "g++ -shared"

# For clang/llvm scan-build analyzer
setenv CCC_CC $GNU_BIN/gcc
setenv CCC_CC $GNU_BIN/g++

setenv COMPILER   gcc
setenv CMAKE_C_COMPILER $GNU_BIN/gcc
setenv CMAKE_CXX_COMPILER $GNU_BIN/g++

proc ModulesHelp { } {
        puts stderr "\t makes gcc, g++ and friends use gnu snapshot (16)"
        puts stderr ""
}
--------------------------

This way I keep all the settings for gcc-16 together,
and can switch from the system compiler with:
  	module load gcc/_standalone
and back with
  	module unload gcc

(There is also a command "ml" in package module-assistant which
  allows an even shorter syntax for loading and unloading modules.)

You may notice the reference to an llvm module
- that alloww me to switch compiler to clang/clang++ to check my code against 
a second compiler ...

I dont appear to be changing LD_LIBRARY_PATH or LIBRARY_PATH
- iirc the right way to do that is with -rpath=... and similar linker options 
(use -Wl,option when setting from the compiler options)
but you can set them with setenv,  prepend-path and append-path, eg
append-path LIBRARY_PATH /usr/lib/x86_64-linux-gnu:/lib/x86_64-linux-gnu

-- 
Andrew C. Aitchison                      Kendal, UK
                    andrew at aitchison.me.uk