setlocal EnableDelayedExpansion in Makefile (Microsoft Windows)

Question

src/Makefile

SHELL := cmd.exe

target:
    setlocal EnableDelayedExpansion
    set foo=hello
    echo !foo! %foo%

run the target

cd src
mingw32-make.exe
// output: !foo!

Why setlocal EnableDelayedExpansion not work in Makefile ?

mingw32-make.exe --version
GNU Make 3.82.90
Built for i686-pc-mingw32

Answer 1

Each action in a recipe is executed in separate shell. It means, that your recipe is equivalent of a shell script:

cmd.exe /c setlocal EnableDelayedExpansion
cmd.exe /c set foo=hello
cmd.exe /c echo !foo! %foo%

There are two ways to execute a recipe in one shell invocation.

First, is you can either write a multi line:

target:
    setlocal EnableDelayedExpansion \
    set foo=hello                   \
    echo !foo! %foo%

Another way to do recipe in one shell is to use a special target .ONESHELL Then your makefile can be

.ONESHELL:
target:
    setlocal EnableDelayedExpansion
    set foo=hello
    echo !foo! %foo%

Both approaches have limitations and caveats described in documentation. Choose what approach is better for you and your case.