pkgs/epicsSetupHook: init to specify EPICS build instructions

This uses the setup hook system,
which is mostly bash,
which should be easier to understand.

pkgs/build-support/epics-setup-hook/default.nix

@@ -0,0 +1,28 @@
+{
+  makeSetupHook,
+  stdenv,
+  epnixLib,
+}:
+makeSetupHook {
+  name = "epics-setup-hook";
+
+  substitutions = {
+    # Note that since the setup hook is going into 'nativeBuildInputs',
+    # the platforms are "shifted",
+    # which means from the point of view of the setup hook,
+    # the host platform is the end package's build platform,
+    # and the target platform is the end package's host platform.
+
+    # "build" as in Nix terminology (the build machine)
+    build_arch = epnixLib.toEpicsArch stdenv.hostPlatform;
+    # "host" as in Nix terminology (the machine which will run the generated code)
+    host_arch = epnixLib.toEpicsArch stdenv.targetPlatform;
+  };
+
+  meta = {
+    description = "Instructions for building EPICS tops";
+    maintainers = with epnixLib.maintainers; [minijackson];
+    hidden = true;
+  };
+}
+./epics-setup-hook.sh

pkgs/build-support/epics-setup-hook/epics-setup-hook.sh

@@ -0,0 +1,114 @@
+epicsConfigurePhase() {
+	runHook preConfigure
+
+	if ! [[ -v enableParallelBuilding ]]; then
+		enableParallelBuilding=1
+	fi
+
+	appendToVar makeFlags "INSTALL_LOCATION=$out"
+
+	stripDebugList+=("bin/@host_arch@" "lib/@host_arch@")
+
+	# Ensure reproducibility when running Perl scripts that generate files,
+	# during the build.
+	export PERL_HASH_SEED=0
+
+	# This variable is used as a default version revision if no VCS is found.
+	#
+	# Since fetchgit and related fetchers remove the .git directory for
+	# reproducibility, EPICS fallsback to either the GENVERSIONDEFAULT variable
+	# if set (not the default), or the current date/time, which isn't
+	# reproducible.
+	echo 'GENVERSIONDEFAULT="EPNix"' >configure/CONFIG_SITE.local
+
+	# This prevents EPICS from detecting installed libraries on the host
+	# system, for when Nix is compiling without sandbox (e.g.: WSL2)
+	echo 'GNU_DIR="/var/empty"' >>configure/CONFIG_SITE.local
+
+	if [[ "@build_arch@" != "@host_arch@" ]]; then
+		stripDebugList+=("bin/@build_arch@" "lib/@build_arch@")
+
+		# Tell EPICS we are compiling to the given architecture.
+		# "host" as in Nix terminology (the machine which will run the generated code)
+		echo 'CROSS_COMPILER_TARGET_ARCHS="@host_arch@"' >>configure/CONFIG_SITE.local
+	fi
+
+	echo "${local_config_site-}" >>configure/CONFIG_SITE.local
+
+	# Undefine the SUPPORT variable here, since there is no single "support"
+	# directory and this variable is a source of conflicts between RELEASE files
+	echo "undefine SUPPORT" >configure/RELEASE.local
+
+	echo "${local_release-}" >>configure/RELEASE.local
+
+	# set to empty if unset
+	: "''${EPICS_COMPONENTS=}"
+
+	# For each EPICS-specific package (e.g. asyn, StreamDevice),
+	# add it to the 'configure/RELEASE.local' file
+	IFS=: read -ra components <<<"$EPICS_COMPONENTS"
+	for component in "${components[@]}"; do
+		echo "$component" >>configure/RELEASE.local
+	done
+
+	echo "=============================="
+	echo "CONFIG_SITE.local"
+	echo "------------------------------"
+	cat "configure/CONFIG_SITE.local"
+	echo "=============================="
+	echo "RELEASE.local"
+	echo "------------------------------"
+	cat "configure/RELEASE.local"
+	echo "------------------------------"
+
+	runHook postConfigure
+}
+
+if [ -z "${dontUseEpicsConfigure-}" ] && [ -z "${configurePhase-}" ]; then
+	configurePhase=epicsConfigurePhase
+fi
+
+epicsInstallPhase() {
+	runHook preInstall
+
+	# Don't do a manual `make install`, `make` already installs
+	# everything into `INSTALL_LOCATION`.
+
+	runHook postInstall
+}
+
+if [ -z "${dontUseEpicsInstall-}" ] && [ -z "${installPhase-}" ]; then
+	installPhase=epicsInstallPhase
+fi
+
+# Automatically create binaries directly in `bin/` that calls the ones that
+# are in `bin/linux-x86_64/`
+# TODO: we should probably do the same for libraries
+epicsInstallProgramsHook() {
+	echo "Installing programs in 'bin/@host_arch@' to 'bin'..."
+	if [[ -d "$out/bin/@host_arch@" ]]; then
+		for file in "$out/bin/@host_arch@/"*; do
+			[[ -x "$file" ]] || continue
+
+			echo "Installing program '$(basename "$file")' to 'bin'"
+			makeWrapper "$file" "$out/bin/$(basename "$file")"
+		done
+	fi
+}
+
+if [ -z "${dontInstallPrograms-}" ]; then
+	postInstallHooks+=(epicsInstallProgramsHook)
+fi
+
+epicsInstallIocBootHook() {
+	if [[ -d iocBoot ]]; then
+		echo "Installing 'iocBoot' folder..."
+		cp -rafv iocBoot -t "$out"
+	else
+		echo "No 'iocBoot' folder found, skipping"
+	fi
+}
+
+if [ -z "${dontInstallIocBoot-}" ]; then
+	postInstallHooks+=(epicsInstallIocBootHook)
+fi

pkgs/default.nix

@@ -61,6 +61,8 @@ in
       };
       epics-base = self.epics-base7;
 
+      epicsSetupHook = callPackage ./build-support/epics-setup-hook {};
+
       # EPICS support modules
 
       support = recurseExtensible (_self: {