cpiker · Oct 29, 2026 · Oct 29, 2026
diff --git a/.github/workflows/emscripten.yml b/.github/workflows/emscripten.yml
@@ -0,0 +1,68 @@
+# Build das2C for WebAssembly with buildfiles/emscripten.mak on Ubuntu 24.04
+# and run the wasm test programs under node.  Regression testing only:
+# nothing is uploaded, the wasm archive is not a release file.  das2js is
+# the downstream that links it into a browser module.  release.yml still
+# calls this workflow and publishes nothing unless it passes.
+#
+# The wasm output doesn't depend on the host, so the runner OS only decides
+# how the toolchain gets installed.  Pinned like ubuntu.yml, so the build
+# changes only when this file does.
+#
+# emsdk is cloned and installed directly rather than through a marketplace
+# action, the same steps notes/build_for_emscripten.md gives a developer.
+# EMSDK_VER pins emscripten itself; bump it here to move CI to a new
+# compiler.  emsdk_env.sh sets PATH and EMSDK_NODE for one shell only, so
+# every step that needs emcc or node sources it.
+#
+# Nothing is cached.  emscripten.mak downloads and builds expat and FFTW on
+# every run, which is what keeps the pinned URLs and SHA-256 sums honest:
+# a release that moves or changes upstream fails here first.  FFTW is the
+# slow part of the run.
+
+name: Emscripten
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  workflow_dispatch:
+  workflow_call:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-24.04
+
+    env:
+      EMSDK_VER: 6.0.13
+
+    defaults:
+      run:
+        shell: bash
+
+    steps:
+      - uses: actions/checkout@v7
+
+      - name: Install emsdk
+        run: |
+          git clone --depth 1 https://github.com/emscripten-core/emsdk.git "$RUNNER_TEMP/emsdk"
+          cd "$RUNNER_TEMP/emsdk"
+          ./emsdk install "$EMSDK_VER"
+          ./emsdk activate "$EMSDK_VER"
+
+      # Separate from the test step, so a failure says whether it was the
+      # dependency downloads, the compile or the link.  -j reaches the expat
+      # and FFTW builds too, see the expat rule in emscripten.mak.
+      - name: Build
+        run: |
+          source "$RUNNER_TEMP/emsdk/emsdk_env.sh"
+          emcc --version
+          make -j"$(nproc)" -f buildfiles/emscripten.mak build_test
+
+      - name: Test
+        run: |
+          source "$RUNNER_TEMP/emsdk/emsdk_env.sh"
+          make -f buildfiles/emscripten.mak test
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
@@ -12,7 +12,8 @@
 #   das2C-<ver>-macos<N>-arm64.tar.gz     The same for Apple Silicon
 #
 # The builds themselves are windows.yml, ubuntu.yml and macos.yml, which
-# also run on every push to master.
+# also run on every push to master.  emscripten.yml runs too, though it
+# ships nothing: a release waits on the wasm tests like the others.
 # A tag with a '-' in it, such as v3.0-pre8, makes a pre-release.  Any other
 # tag must match "version-string" in vcpkg.json, so a release can't go out
 # with a mismatched version number.  Nothing is published unless every build
@@ -78,8 +79,12 @@ jobs:
     with:
       version: ${{ needs.check.outputs.version }}
 
+  emscripten:
+    needs: check
+    uses: ./.github/workflows/emscripten.yml
+
   publish:
-    needs: [ check, windows, ubuntu, macos ]
+    needs: [ check, windows, ubuntu, macos, emscripten ]
     runs-on: ubuntu-latest
     permissions:
       contents: write

diff --git a/.gitignore b/.gitignore
@@ -1,4 +1,5 @@
 build.*/
+deps.*/
 build/
 *.obj
 buildfiles/nbproject/private

diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -15,7 +15,7 @@
 #   cmake --install build.cmake/default --prefix C:\opt
 #   cmake --build --preset default --target uninstall
 #
-# On Windows the programs run on das3.dll, as with Windows.mak.  Elsewhere
+# On Windows the programs run on das3.dll, as with windows.mak.  Elsewhere
 # they link the static library, use the "dll" preset to add libdas3.so.
 # Without presets, pass
 # -DCMAKE_TOOLCHAIN_FILE=%VCPKG_ROOT%/scripts/buildsystems/vcpkg.cmake, or
@@ -74,7 +74,7 @@ if(CMAKE_HOST_WIN32 AND CMAKE_GENERATOR MATCHES "Ninja" AND NOT DEFINED CMAKE_C_
 endif()
 
 # Static vcpkg dependencies built for the DLL C runtime (/MD) by default on
-# Windows, the same as Windows.mak, so they all land in das3.dll.  Must be set
+# Windows, the same as windows.mak, so they all land in das3.dll.  Must be set
 # before project().  The C runtime is CMake's default, /MD, except with a
 # fully static triplet such as x64-windows-static, see below.  Without vcpkg,
 # as under conda, /MD matches the dependency DLLs.
@@ -94,7 +94,7 @@ include(CMakePackageConfigHelpers)
 
 option(DAS_WITH_SPICE "Build the SPICE programs" ON)
 option(DAS_WITH_CDF "Build the CDF programs" ON)
-# On Windows the programs run on das3.dll, as with Windows.mak, so that the
+# On Windows the programs run on das3.dll, as with windows.mak, so that the
 # dependencies are in the DLL once instead of in every program.  Elsewhere
 # they link the static library, as with Linux.mak.
 if(WIN32)
@@ -179,7 +179,7 @@ endif()
 
 # The makefiles keep assert() active in optimized builds and so do we.  For
 # MSVC also put debug info in the objects (/Z7) so libdas3.lib carries it,
-# leave inlining at the /O2 level as Windows.mak does, and skip incremental
+# leave inlining at the /O2 level as windows.mak does, and skip incremental
 # linking, which leaves 20 MB+ .ilk files.  Linking with /debug turns off
 # removal of unused code, so optimized builds ask for it back (/OPT).
 foreach(_cfg RELEASE RELWITHDEBINFO MINSIZEREL)

diff --git a/Makefile b/Makefile
@@ -20,12 +20,6 @@ ifeq ($(INST_DOC),)
 INST_DOC=$(INST_SHARE)/doc
 endif
 
-# Cross compiling to WebAssembly: objects land in build.wasm32 and the
-# emscripten rules below replace the host platform's
-ifeq ($(EMSCRIPTEN),yes)
-N_ARCH=wasm32
-endif
-
 ifeq ($(N_ARCH),)
 N_ARCH=/
 #N_ARCH=$(shell uname).$(shell uname -m)
@@ -46,10 +40,8 @@ endif
 
 # SPICE and CDF programs are part of the standard build, SPICE=no or CDF=no
 # leaves them out (so does any value but "yes").
-ifneq ($(EMSCRIPTEN),yes)
 SPICE?=yes
 CDF?=yes
-endif
 
 BLD_CSPICE=0
 ifeq ($(SPICE),yes)
@@ -79,6 +71,11 @@ C_HDR_DIR:=$(CURDIR)
 BUILD_DIR:=build.$(N_ARCH)
 C_BUILD_DIR:=$(CURDIR)/$(BUILD_DIR)
 
+# Downloaded sources and the dependency builds made from them (CDF, CSPICE).
+# Beside the build directory rather than in it, so clean can remove all of
+# $(BUILD_DIR) and only distclean costs a re-download.
+DEPS_DIR:=deps.$(N_ARCH)
+
 ##############################################################################
 # Native Platform specific include
 
@@ -100,9 +97,14 @@ export INST_NAT_LIB
 export C_BUILD_DIR
 export C_HDR_DIR
 
-ifeq ($(EMSCRIPTEN),yes)
-$(info Cross compiling for wasm32 with emscripten)
-include buildfiles/Emscripten.mak
-else
+# The WebAssembly build is not selected here, use:
+#
+#   make -f buildfiles/emscripten.mak
+#
+# The windows build is not selected here either, use:
+#
+#   nmake /f buildfiles\windows.mak
+#   -or-
+#   cmake --preset default
+
 include buildfiles/$(UNAME).mak
-endif
diff --git a/README.md b/README.md
@@ -98,15 +98,16 @@ For a WebAssembly build of the library alone (no utilities), with emscripten's
 emsdk activated in the shell:
 
 ```bash
-$ make EMSCRIPTEN=yes EXPAT_INC=/path/to/expat/lib build
-$ make EMSCRIPTEN=yes EXPAT_INC=/path/to/expat/lib EXPAT_LIB=/path/to/libexpat.a test
+$ make -f buildfiles/emscripten.mak
+$ make -f buildfiles/emscripten.mak test
+
+# To rebuild
+$ make -f buildfiles/emscripten.mak clean     # Removes only das2C output
+$ make -f buildfiles/emscripten.mak distclean # Removes expat and FFTW as well
 ```
 
-Output lands in `build.wasm32/`.  Emscripten provides zlib but not expat, so a
-libexpat built for wasm32 has to be supplied.  See
-[notes/build_for_emscripten.md](notes/build_for_emscripten.md) for the
-toolchain setup, what is left out of the archive and why, and how to link
-the result into a program of your own.
+Output lands in `build.wasm32/`.  The build expat and fftw and builds them
+for wasm32 under `deps.wasm32/`.  See [notes/build_for_emscripten.md](notes/build_for_emscripten.md) for the toolchain setup.
 
 For Windows systems issue the following commands in a command shell to build
 and test the software.  Dependencies are installed by [vcpkg](https://vcpkg.io)
@@ -117,8 +118,8 @@ See [notes/build_for_windows.md](notes/build_for_windows.md) for details.
 > vcvars64.bat              ::puts nmake.exe, cl.exe, link.exe, etc. on your path
 > set VCPKG_ROOT=           ::location of your vcpkg clone
 
-> nmake /f buildfiles\Windows.mak SPICE=yes CDF=yes
-> nmake /f buildfiles\Windows.mak SPICE=yes CDF=yes test
+> nmake /f buildfiles\windows.mak
+> nmake /f buildfiles\windows.mak test
 ```
 
 On Windows you can also build with [CMake](https://cmake.org), which Visual
@@ -128,9 +129,8 @@ tested on Windows so far.
 
 ```batchfile
 > vcvars64.bat
-> set VCPKG_ROOT=           ::location of your vcpkg clone
-
-> cmake --preset default            ::configure, vcpkg builds the dependencies
+> set VCPKG_ROOT=                 ::location of your vcpkg clone
+> cmake --preset default          ::configure step, vcpkg builds the dependencies
 > cmake --build --preset default
 > ctest --preset default
 ```
@@ -149,10 +149,10 @@ $ make PREFIX=/usr/local install   # adjust destination to taste
 ```
 or on Windows:
 ```batch
-nmake /f buildfiles\Windows.mak PREFIX=C:\local install  
+nmake /f buildfiles\windows.mak PREFIX=C:\opt install  
 ```
 ```batch
-cmake --install build.cmake\default --prefix C:\local
+cmake --install build.cmake\default --prefix C:\opt
 ```
 
 > **Side note:** a CMake install can be undone with

diff --git a/buildfiles/Android.mak b/buildfiles/Android.mak
@@ -25,6 +25,12 @@ TEST_PROGS=TestUnits TestArray TestDs TestBuilder \
  TestV3Read TestProp TestIter TestUri TestFilter TestValue TestRaggedEncode \
  TestGen TestForm TestCplx TestVar TestVarSubset TestDim TestDatum
 
+# Set by the top level Makefile, which includes this file.  Read on its own
+# (make -f) every output path would start at /, so refuse.
+ifeq ($(BUILD_DIR),)
+$(error buildfiles/Android.mak is included by Makefile, run make from the top of the source tree)
+endif
+
 BD=$(BUILD_DIR)
 
 ##############################################################################

diff --git a/buildfiles/Darwin.mak b/buildfiles/Darwin.mak
@@ -19,10 +19,13 @@
 #      tools.
 #
 #   CSPICE:  From CSPICE_INC and CSPICE_LIB when set, otherwise the NAIF
-#      toolkit for this machine's architecture is downloaded to $(BD)/cspice
+#      toolkit for this machine's architecture is downloaded to
+#      $(DEPS_DIR)/cspice
 #
 #   CDF:  From CDF_INC and CDF_LIB when set, otherwise the SPDF source
-#      distribution is downloaded and built under $(BD)
+#      distribution is downloaded and built under $(DEPS_DIR)
+#
+#   Only distclean removes $(DEPS_DIR), clean leaves the downloads alone.
 #
 # Apple's clang honors MACOSX_DEPLOYMENT_TARGET from the environment, set it
 # to build for older MacOS versions than the one running the build.  Static
@@ -32,6 +35,12 @@
 MD5SUM=md5 -r
 export MD5SUM
 
+# Set by the top level Makefile, which includes this file.  Read on its own
+# (make -f) every output path would start at /, so refuse.
+ifeq ($(BUILD_DIR),)
+$(error buildfiles/Darwin.mak is included by Makefile, run make from the top of the source tree)
+endif
+
 BD=$(BUILD_DIR)
 
 ##############################################################################
@@ -52,8 +61,8 @@ LOC_CDF_ENV:=x86_64
 endif
 
 ifeq ($(BLD_CDF),1)
-CDF_INC:=$(BD)/$(LOC_CDF_DIST)/src/include
-CDF_LIB:=$(BD)/$(LOC_CDF_DIST)/src/lib/libcdf.a
+CDF_INC:=$(DEPS_DIR)/$(LOC_CDF_DIST)/src/include
+CDF_LIB:=$(DEPS_DIR)/$(LOC_CDF_DIST)/src/lib/libcdf.a
 endif
 
 # Downstream packages (das2py) take libcdf.dylib from $(BD) so that they run
@@ -66,8 +75,8 @@ CDF_SO_REDIST:=$(BD)/libcdf.dylib
 endif
 
 ifeq ($(BLD_CSPICE),1)
-CSPICE_INC:=./$(BD)/cspice/include
-CSPICE_LIB:=./$(BD)/cspice/lib/cspice.a
+CSPICE_INC:=./$(DEPS_DIR)/cspice/include
+CSPICE_LIB:=./$(DEPS_DIR)/cspice/lib/cspice.a
 endif
 
 
@@ -76,7 +85,7 @@ endif
 
 TARG=libdas3
 
-# File lists are shared with Linux.mak and Windows.mak, add new sources there
+# File lists are shared with Linux.mak and windows.mak, add new sources there
 include buildfiles/sources.mak
 
 SRCS:=$(notdir $(LIB_SRCS))
@@ -239,6 +248,10 @@ $(BD):
 	@if [ ! -e "$(BD)" ]; then echo mkdir $(BD); \
         mkdir $(BD); chmod g+w $(BD); fi
 
+$(DEPS_DIR):
+	@if [ ! -e "$(DEPS_DIR)" ]; then echo mkdir $(DEPS_DIR); \
+        mkdir $(DEPS_DIR); chmod g+w $(DEPS_DIR); fi
+
 # Records which objects make up the library.  A source dropped from the list
 # changes that set without making any object newer than the archive, so make
 # alone would keep a stale one.  The file is rewritten only when the set
@@ -301,8 +314,8 @@ endif
 
 build_dep:$(_DEPS)
 
-$(CSPICE_LIB): $(BD)/cspice.tar
-	cd $(BD) && tar -mxf cspice.tar
+$(CSPICE_LIB): $(DEPS_DIR)/cspice.tar
+	cd $(DEPS_DIR) && tar -mxf cspice.tar
 
 # Checked on every build, see the same rule in Linux.mak for why
 ifeq ($(BLD_CDF),1)
@@ -321,20 +334,20 @@ $(CDF_SO_REDIST): FORCE | $(BD)
 		echo "cp $(CDF_SO) $@"; cp "$(CDF_SO)" $@; \
 	fi
 
-$(BD)/cspice.tar: | $(BD)
-	curl -f -L $(LOC_CSPICE_URL) > $(BD)/cspice.tar.Z
-	uncompress $(BD)/cspice.tar.Z
+$(DEPS_DIR)/cspice.tar: | $(DEPS_DIR)
+	curl -f -L $(LOC_CSPICE_URL) > $(DEPS_DIR)/cspice.tar.Z
+	uncompress $(DEPS_DIR)/cspice.tar.Z
 
 # CDF's own tools need curses, the library does not.  Without a full Xcode
 # install the CDF makefile prints xcodebuild errors while probing for an Xcode
 # version, these are harmless.
-$(CDF_LIB): $(BD)/$(LOC_CDF_DIST)
-	cd $(BUILD_DIR)/$(LOC_CDF_DIST) && $(MAKE) OS=macosx ENV=$(LOC_CDF_ENV) \
+$(CDF_LIB): $(DEPS_DIR)/$(LOC_CDF_DIST)
+	cd $(DEPS_DIR)/$(LOC_CDF_DIST) && $(MAKE) OS=macosx ENV=$(LOC_CDF_ENV) \
 	 CURSES=no FORTRAN=no all
 
-$(BD)/$(LOC_CDF_DIST): | $(BD)
-	curl -f -L $(LOC_CDF_URL) > $(BD)/$(LOC_CDF_DIST)-cdf.tar.gz
-	cd $(BD) && tar -xf $(LOC_CDF_DIST)-cdf.tar.gz
+$(DEPS_DIR)/$(LOC_CDF_DIST): | $(DEPS_DIR)
+	curl -f -L $(LOC_CDF_URL) > $(DEPS_DIR)/$(LOC_CDF_DIST)-cdf.tar.gz
+	cd $(DEPS_DIR) && tar -xf $(LOC_CDF_DIST)-cdf.tar.gz
 
 # Run tests
 
@@ -529,13 +542,12 @@ $(INST_DOC)/das2C:$(BD)/html
 
 
 # Cleanup ####################################################################
-distclean:
+# Same split as Linux.mak: all of $(BD) is ours, $(DEPS_DIR) costs a re-fetch
+clean:
 	if [ -d "$(BD)" ] ; then rm -r $(BD) ; fi
 
-clean:
-	-rm $(BD)/das* $(BD)/Test* $(BD)/libdas*
-	-rm $(BD)/*.o $(BD)/*.d $(BD)/ex*
-	-rm $(BD)/cred_test*
+distclean: clean
+	if [ -d "$(DEPS_DIR)" ] ; then rm -r $(DEPS_DIR) ; fi
 
 
 ## Automatic dependency tree generation for C code ###########################