5f47cb8c328b76c41a9a21599477bfacf4d91a37
braney
  Sun Sep 6 16:57:16 2026 -0700
makefiles: let the compiler write the header dependencies

The tree had 72 hand-written "foo.o: bar.h" lines across 15 makefiles, so
almost every object was rebuilt only when its own .c file changed.  Editing a
header left every other object that included it holding the old layout, and the
crash landed somewhere the change never touched.

The %.o: %.c rule in inc/common.mk now passes -MMD -MP.  The compiler writes
foo.d beside foo.o listing the headers that compile really read, and an
-include reads them back.  Nine makefiles keep a compile rule of their own,
because they add -DGBROWSE, -DGFSERVER_HUGE or -DCGI_BIN=; each got ${DEPGEN}
too.  lib and hg/lib are the only two that build objects into a subdirectory,
and each reads its own subdirectory .d files at the foot of its own file.

Touching hg/hgTracks/wigCommon.h used to rebuild 2 objects.  It now rebuilds
11, which is every .c file in that directory that includes the header.

A .d file holds rules, and make takes its default goal from the first rule it
reads, included files and all.  common.mk is read before a makefile's own
rules, so the include has to save $(.DEFAULT_GOAL) and set it back afterwards;
without that, make in lib built adjacency.o and stopped.

Fifteen link rules in directories the build enters named a library on the
command line without depending on it.  Each now lists it.  hg/hgPhyloPlace,
hg/visiGene/hgVisiGene and hg/orthoMap were the three whose target is a real
file and could go stale.

make clean still leaves the .d files.  A shared clean:: rule in common.mk would
first mean converting about 320 single-colon clean: rules, since make refuses
to mix the two forms on one target.  A leftover .d cannot break a build: -MP
writes an empty target for each header, so a deleted or renamed one does not
leave make asking for a file no rule can build.

refs #36621

diff --git src/lib/makefile src/lib/makefile
index b4970495428..c95a861d36a 100644
--- src/lib/makefile
+++ src/lib/makefile
@@ -58,15 +58,21 @@
 reEncodeFont.c:   reEncodeFont.ps
 	${STRINGIFY} -static -var=encodeFont reEncodeFont.ps > reEncodeFont.c || rm reEncodeFont.c
 
 $(MACHTYPE):
 	mkdir -p $(MACHTYPE)
 
 test:
 	cd tests && ${MAKE} test
 
 clean:
 	rm -f ${O} $(MACHTYPE)/jkweb.a
 	cd tests && ${MAKE} clean
 
 tags:
 	etags ../inc/*.h ../lib/*.h ../lib/*.c  ../hg/inc/*.h ../hg/lib/*.h ../hg/lib/*.c ../hg/hgTracks/*.c ../hg/hgc/*.c ../hg/hgTrackUi/*.c
+
+# The objects in the subdirectories need their generated header dependencies
+# too, and common.mk only looks in the current directory.  This sits at the foot
+# of the file so the rules it brings in cannot become the default goal.
+# refs #36621
+-include $(wildcard font/*.d)