Things I always forgot

• Use double dollar sign ‘$$’ to reference Bash environment variable/evaluation.

Tips for writing shell scripts within makefiles

• Escape the script’s use of $ by replacing with $$
• Convert the script to work as a single line by inserting ; between commands
• If you want to write the script on multiple lines, escape end-of-line with \
• Optionally start with set -e to match make’s provision to abort on sub-command failure
• This is totally optional, but you could bracket the script with () or {} to emphasize the cohesiveness of a multiple line sequence – that this is not a typical makefile command sequence

Here’s an example inspired by the OP:

mytarget:
    { \
    set -e ;\
    msg="header:" ;\
    for i in $$(seq 1 3) ; do msg="$$msg pre_$${i}_post" ; done ;\
    msg="$$msg :footer" ;\
    echo msg=$$msg ;\
    }

System wide C++ change on Ubuntu:

Clang produces better error messages GCC has much better and more complete support for C++11 features

sudo update-alternatives --config c++