On Fri, Mar 13, 2020 at 10:49 PM Bruno Haible <bruno@xxxxxxxxx> wrote: >> but when something goes > > wrong, the poor schmuck who has to debug it wants to know that it was > > the test for `ceil` (for instance) that hung the build, not the > > unrelated thing that happens to have been tested right before that. > > Hanging autoconf tests are rare. And even in that case, looking at > the configure output does not help much, because it won't tell you > whether the compiler is taking hours or whether the test program hangs. > In practice, when something hangs, "ps aux" or "pstree -p" (when available) > is a better starting point for debugging. Aha, you're coming at this from the perspective of debugging with interactive access to the system where the problem happens. All of the worst autoconf-related bugs I've had to deal with in the past decade or so, showed up in CI environments that I did _not_ have interactive access to. I only got the transcript of the build. I had to specifically add code to dump the contents of config.log, and then track things down further by adding extra AC_MSG_* within the problem macro. You can probably imagine how frustrating this can be, especially when the cycle time is a half-hour or more. I haven't had to deal with any of these problems with a project that made heavy use of gnulib, but I would have been quite annoyed to find that I was barking up the wrong tree because configure didn't tell me that it was doing some check because it didn't seem important enough. Also, overriding $as_echo(_n), and your suggestion to override AS_ECHO_N with pushdef, are more problematic than you may realize because they affect what gets written to config.log, not just what gets written to configure's stderr. (Because configure writes to config.log with a construct like AS_ECHO([...]) >&AS_MESSAGE_LOG_FD.) May I suggest that what you really want is a --quiet switch for configure, a la V=0 with automake-generated makefiles? If you had that, would you be OK with changing all of the gnulib .m4 files that currently use gl_AC_CACHE_VAL_SILENT to use AC_CACHE_CHECK instead? zw
