I forgot to use the stamp trick on bison generated files, the very next patch will do it. Index: ChangeLog from Benoît Perrot &lt;benoit(a)lrde.epita.fr&gt; Do not update timestamps of generators when they fail. * src/parse/Makefile.am, dev/inst-makefile-gen.py: Suggested by Akim Demaille: Read Automake.texi :) Index: src/parse/Makefile.am --- src/parse/Makefile.am (revision 130) +++ src/parse/Makefile.am (revision 131) @@ -13,17 +13,22 @@ asm-parse.yy parse-asm-parse.stamp \ $(FROM_ASM_PARSE_YY) +# This code comes from "Handling Tools that Produce Many Outputs", +# from the Automake documentation. + parse-asm-scan.stamp: $(top_srcdir)/dev/parse-asm-scan-gen.py $(top_srcdir)/dev/nolimips.xml + @rm -rf $@.tmp + @touch $@.tmp $(top_srcdir)/dev/parse-asm-scan-gen.py < $(top_srcdir)/dev/nolimips.xml - touch $@ + @mv -f $@.tmp $@ asm-scan.ll: parse-asm-scan.stamp - touch $@ parse-asm-parse.stamp: $(top_srcdir)/dev/parse-asm-parse-gen.py $(top_srcdir)/dev/nolimips.xml + @rm -rf $@.tmp + @touch $@.tmp $(top_srcdir)/dev/parse-asm-parse-gen.py < $(top_srcdir)/dev/nolimips.xml - touch $@ + @mv -f $@.tmp $@ asm-parse.yy: parse-asm-parse.stamp - touch $@ $(FROM_ASM_PARSE_YY): $(srcdir)/asm-parse.yy bison -S lalr1.cc -d -ra $(srcdir)/asm-parse.yy -o asm-parse.cc Index: dev/inst-makefile-gen.py --- dev/inst-makefile-gen.py (revision 130) +++ dev/inst-makefile-gen.py (revision 131) @@ -50,20 +50,28 @@ program_builder.hh inst-builder-gen.stamp \\ program_solver.hh program_solver.cc inst-solver-gen.stamp +# This code comes from \"Handling Tools that Produce Many Outputs\", +# from the Automake documentation. inst-nodes-gen.stamp: $(top_srcdir)/dev/inst-nodes-gen.py $(top_srcdir)/dev/nolimips.xml + @rm -rf $@.tmp + @touch $@.tmp $(top_srcdir)/dev/inst-nodes-gen.py < $(top_srcdir)/dev/nolimips.xml - touch $@ + @mv -f $@.tmp $@ $(FROM_INST_NODES_GEN_PY): inst-nodes-gen.stamp inst-builder-gen.stamp: $(top_srcdir)/dev/inst-builder-gen.py $(top_srcdir)/dev/nolimips.xml + @rm -rf $@.tmp + @touch $@.tmp $(top_srcdir)/dev/inst-builder-gen.py < $(top_srcdir)/dev/nolimips.xml - touch $@ + @mv -f $@.tmp $@ program_builder.hh: inst-builder-gen.stamp inst-solver-gen.stamp: $(top_srcdir)/dev/inst-solver-gen.py $(top_srcdir)/dev/nolimips.xml + @rm -rf $@.tmp + @touch $@.tmp $(top_srcdir)/dev/inst-solver-gen.py < $(top_srcdir)/dev/nolimips.xml - touch $@ + @mv -f $@.tmp $@ program_solver.hh program_solver.cc: inst-solver-gen.stamp