Hi Paul, On 2023-08-26 18:48, Paul Smith wrote: > I added a new appendix to the GNU make manual for troubleshooting help; > I haven't pushed it yet. See below. Comments welcome. > > I think the outline you provided earlier, Bruno, has the problem that a > lot of it isn't really about troubleshooting per se, it's about how to > write makefiles in general. I tried to restrict this specifically to > describing the types of problems you might see and the steps you might > take to troubleshoot them. > > I'm thinking of adding another chapter on hints and tips for writing > good makefiles. > > ----------------- > Appendix C Troubleshooting Make and Makefiles > ********************************************* > > Troubleshooting 'make' and makefiles can be tricky. There are two > reasons: first, makefiles are not procedural programs and many users are > used to procedural languages and scripts. Second, makefiles consist of > two different syntaxes in one file: makefile syntax, that 'make' reads, > and shell syntax, which is sent to a shell program for parsing and > execution. > > If you have problems with GNU Make, first consider the type of > problem you are having. Problems will generally be in one of these > categories: > > * A syntax or other error was reported when 'make' attempted to parse > your makefiles. > > * A command that 'make' invoked failed (exited with a non-0 exit > code). > > * The command that 'make' invoked was not the one you expected. > > * 'make' was not able to find a rule to build a target. > > * 'make' rebuilds a target that you didn't think was out of date. > > * Or, 'make' did not rebuild a target that you expected it to build. > > The strategies for troubleshooting differ for different types of > problems. For issues related to how makefiles are parsed, strategies > include: > > * Using the '-p' option to show the makefile database, after > evaluation (*note Summary of Options: Options Summary.). > > * Using the 'info' function to understand how elements of the > makefile are expanded (*note Functions That Control Make: Make > Control Functions.). > > For issues related to how rules are applied, strategies include: > > * Removing the '@' prefix from recipes, so you can see the commands > make is invoking to rebuild the target (*note Recipe Echoing: > Echoing.). > > * Using the '--trace' option to explain which rules 'make' invokes > and why (*note Summary of Options: Options Summary.). > > * Using the '--debug=v,i' or '-d' options to show how 'make' is > determining which recipes should be used, or why targets do not > need to be rebuilt (*note Summary of Options: Options Summary.). > > * Menu: > > * Parse Error:: Syntax errors when parsing makefiles. > * Command Failure:: Recipe commands exit with error codes. > * Wrong Rule:: 'make' chooses the wrong rule. > * No Rule Found:: No rule was found to build a target. > * Extra Rebuilds:: Targets are rebuilt unnecessarily. > * Missing Rebuilds:: Out-of-date targets are not rebuilt. > * Troubleshooting Strategies:: Strategies used for troubleshooting issues. > > > C.1 Errors When Parsing Makefiles > ================================= > > This type of error is the simplest to resolve. The error output you > will see will have a format like this: > > Makefile:10: *** missing separator. Stop. > > This message gives you all the information you need to address the > error: it gives the name of the makefile (here 'Makefile') and the line > number (here '10') in that makefile where GNU Make's parser failed. > Following that is a description of the error. Further explanations of > these error messages can be found in *note Errors Generated by Make: > Error Messages. >
When using .SECONDEXPANSION, this becomes a bit more tricky. It would be interesting to recommend to put an $(info $(SUSPECT_VARIABLE)) right before lines where you don't see the issue at first glance. You already mention $(info) in the overview above, but I think a reminder here might be useful. Cheers, Alex -- <http://www.alejandro-colomar.es/> GPG key fingerprint: A9348594CE31283A826FBDD8D57633D441E25BB5
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