Add a prologue which enforces the use of bash

kgryte · kgryte · commit ed739bafcb21 · 2017-09-06T18:37:59.000-07:00
diff --git a/tools/make/Makefile b/tools/make/Makefile
@@ -1,4 +1,52 @@
 
+# VARIABLES #
+
+# Instruct make to warn us when we use an undefined variable (e.g., misspellings).
+MAKEFLAGS += --warn-undefined-variables
+
+# Define the default target:
+.DEFAULT_GOAL := all
+
+# Define the `SHELL` variable to avoid issues on systems where the variable may be inherited from the environment.
+#
+# ## Notes
+#
+# * We use `bash` so that we can use `pipefail`.
+#
+#
+# [1]: https://www.gnu.org/prep/standards/html_node/Makefile-Basics.html#Makefile-Basics
+# [2]: http://clarkgrubb.com/makefile-style-guide
+SHELL := bash
+
+# Define shell flags.
+#
+# ## Notes
+#
+# * `.SHELLFLAGS` was introduced in GNU Make 3.82 and has no effect on the version of GNU Make installed on Mac OS X, which is 3.81.
+# * The `-e` flag causes `bash` to exit immediately if a `bash` executed command fails.
+# * The `-u` flag causes `bash` to exit with an error message if a variable is accessed without being defined.
+# * The `pipefail` option specifies that, if any of the commands in a pipeline fail, the entire pipeline fails. Otherwise the return value of a pipeline is the return value of the last command.
+# * The `-c` flag is in the default value of `.SHELLFLAGS`, which must be preserved, as this is how `make` passes the script to be executed to `bash`.
+#
+.SHELLFLAGS := -eu -o pipefail -c
+
+# Remove targets if its recipe fails.
+#
+# ## Notes
+#
+# * Mentioning this target anywhere in a Makefile prevents a user from re-running make and using an incomplete or invalid target.
+# * When debugging, it may be necessary to comment this line out so the incomplete or invalid target can be inspected.
+#
+# [1]: https://www.gnu.org/software/make/manual/html_node/Special-Targets.html
+.DELETE_ON_ERROR:
+
+# Remove all the default suffixes, preferring to define all rules explicitly.
+#
+# [1]: https://www.gnu.org/software/make/manual/html_node/Suffix-Rules.html#Suffix-Rules
+# [2]: https://www.gnu.org/software/make/manual/html_node/Suffix-Rules.html#Suffix-Rules
+.SUFFIXES:
+
+
 # DEPENDENCIES #
 
 # Order is important:
