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rules.mak: fix module Depend and build rules 

The ../database/database.h dependency is already described (only when
necessary) inside the Depend file for the specific complication unit.
Not all objects are affected by database.h changes, so it doesn't need
to be forced as a dependency for all OBJS.

Depend itself was never rebuilt when a source file changed.  This now
happens, however technically the superior MAKE process needs to restart
so it includes the new updated copy of Depend file we just updated.
However in practice when developing, modifying #include directives does
not happen often and doing 'make; make' will fix the issue performing
an incremental build both times.  So a minor caveat.

Previously when a single source file was changed the entire module was
recompiled, but we have a Depends file to manage the incremental build
problem and we are not really using it (if we always recompile the entire
module due to any one file change, there would be no need for Depends).

Now when developing, a single *.c file change results in the Depends
being rebuilt, then the single file compiled, then the module relinked.
This is exactly the kind of incremental build speedup having a Depends
file is designed to achieve.

Additionally the use of a direct pipeline to create the file does not
manage error scenarios.  MAKE itself is driven by file existance and
their timestamps for targets, so even if 'make depend' failed, it
would still create an output file that MAKE can not distunguish
between a well formed (possibly empty) Depend file and an incorrectly
created partial.  So building in a *.tmp file first and only if all the
commands are successful then rename to target filename.  This has the
effect of making 'make depend' able to fail now.
This commit is contained in:
Darryl L. Miles 2024-10-16 10:49:46 +01:00 committed by R. Timothy Edwards
parent d1ff3671cd
commit bd541d3e6f
1 changed files with 8 additions and 4 deletions
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12
rules.mak
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@ -12,14 +12,18 @@ depend: ${DEPEND_FILE}
# any header (.h) files with an absolute path (beginning with "/"), and
# 3) remove isolated backslash-returns just to clean things up a bit.
${DEPEND_FILE}:
${CC} ${CFLAGS} ${CPPFLAGS} ${DFLAGS} ${DEPEND_FLAG} ${DEPSRCS} | \
sed -e "/#/D" -e "/ \//s/ \/.*\.h//" -e "/ \\\/D" > ${DEPEND_FILE}
# The $$PPID allows this to be run on the same dir in parallel without
# corrupting the output, the final MV is transactional. If that is needed
# it indicates a missing dependency somewhere in a upstream/parent Makefile.
${DEPEND_FILE}: ${DEPSRCS}
${CC} ${CFLAGS} ${CPPFLAGS} ${DFLAGS} ${DEPEND_FLAG} ${DEPSRCS} > ${DEPEND_FILE}$$PPID.tmp
${SED} -e "/#/D" -e "/ \//s/ \/.*\.h//" -e "/ \\\/D" -i ${DEPEND_FILE}$$PPID.tmp
${MV} -f ${DEPEND_FILE}$$PPID.tmp ${DEPEND_FILE}
# Original Depend file generating line:
# ${CC} ${CFLAGS} ${CPPFLAGS} ${DFLAGS} ${DEPEND_FLAG} ${SRCS} > ${DEPEND_FILE}
${OBJS}: %.o: ${SRCS} ../database/database.h
%.o: %.c
@echo --- compiling ${MODULE}/$*.o
${RM} $*.o
${CC} ${CFLAGS} ${CPPFLAGS} ${DFLAGS} -c $*.c