On Fri, 2026-04-03 at 17:34 +0200, R. Diez wrote: > If I modify configure.ac by adding and removing a space character (or > just issue command "touch configure.ac"), files "configure" and > "makefile" are regenerated nevertheless. > > The new contents are identical, but their timestamps change, possibly > triggering a rebuild, depending on the makefile rules.
I am not sure about the details of the current implementation. However, I can imagine a reason why timestamps are updated. If you don't update the timestamps, then every time you run make subsequently autoconf and automake will be re-run again: you invoke make, it sees the files are out of date and runs autoconf/automake, the contents will be checked and found to be identical, and the files will not be updated. Then you run make again, it sees the files are out of date, re-runs autoconf and/or automake, sees the output is identical and does not update the targets. Etc. forever (until you delete the targets or make a change that reflects in the output). Depending on the expense of re-running autoconf / automake compared to the expense of rebuilding that is done when configure and Makefile are modified, it may well be worthwhile to just get it over with the first time.
