@@ -36,6 +36,13 @@ __all:
ifneq ($(sub_make_done),1)
+# Use /bin/bash for repices and $(shell ) invocations.
+SHELL := /bin/bash
+
+# Unlike the other variables, the 'SHELL' is never set from the environment.
+# Use MAKEOVERRIDES to pass 'SHELL' down to sub-makes.
+MAKEOVERRIDES += SHELL=$(SHELL)
+
# Do not use make's built-in rules and variables
# (this increases performance and avoids hard-to-debug behaviour)
MAKEFLAGS += -rR
@@ -1,6 +1,9 @@
# SPDX-License-Identifier: GPL-2.0-only
# Kconfig helper macros
+# Use /bin/bash to evaluate $(shell,) functions
+SHELL := /bin/bash
+
# Convenient variables
comma := ,
quote := "
GNU Make uses /bin/sh by default for running recipe lines and $(shell ), and so does Kconfig for $(shell,...). We are sometimes hit by subtle portability issues like [1] because the code was only tested on systems where /bin/sh is a symlink to bash. One way is to continue whack-a-mole game as somebody will eventually notice that the code is not working on their build environments. Another is a big hammer approach; force bash in the build system so that it works in the same way for everyone. In fact, there exists such a guideline that permits only Bash as the shell scripting language. [2] The kbuild test robot also specifies SHELL=/bin/bash to eliminate the shell portability issue. This commit changes the shell for Make and Kconfig to bash. As the GNU Make manual [3] says, the 'SHELL' is never set from the environment. You cannot do 'export SHELL:=/bin/bash' to propagate it to sub-makes. Instead, use MAKEOVERRIDES to make SHELL:=/bin/bash globally effective. [1]: https://lore.kernel.org/all/20220804190320.262510-1-alexandre.belloni@bootlin.com/ [2]: https://google.github.io/styleguide/shellguide.html [3]: https://www.gnu.org/software/make/manual/html_node/Choosing-the-Shell.html Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- Makefile | 7 +++++++ scripts/Kconfig.include | 3 +++ 2 files changed, 10 insertions(+)