To Whom it May Concern, I may have discovered (and fixed) a bug in the GNU Autoconf suite. The TLDR version is that I think that line 361 of the "autoscan" bash executable needs to be changed from: s/\${[^\}]*}//g; to: s/\$\{[^\}]*}//g;
i.e., the first brace must be escaped. Below I've provided the error messages and information that I hope can be used to replicate the error. I'd love to know if this helps at all, or if you've already discovered it. Please let me know if you need any more info. Thanks so much! James Detailed notes: I was trying to compile W. Richard Stevens' daytimetcpcli.c (Unix Network Programming Vol 1.) I downloaded and extracted autfoconf-2.69 into my downloads folder on my Ubuntu 16.04 VM. I then copied the files daytimetcpcli.c and unp.h to the autofconf folder and ran "make check" and received the following error: ... Autoscan. 503: autoscan FAILED (autoscan.at:44) ## ------------- ## ## Test results. ## ## ------------- ## ERROR: 459 tests were run, 5 failed (4 expected failures). 44 tests were skipped. ## -------------------------- ## ## testsuite.log was created. ## ## -------------------------- ## Please send `tests/testsuite.log' and all information you think might help: To: <bug-autoconf@gnu.org> Subject: [GNU Autoconf 2.69] testsuite: 503 failed You may investigate any problem if you feel able to do so, in which case the test suite provides a good starting point. Its output may be found below `tests/testsuite.dir'. Makefile:596: recipe for target 'check-local' failed make[3]: *** [check-local] Error 1 make[3]: Leaving directory '/home/james/Downloads/autoconf-2.69/tests' Makefile:411: recipe for target 'check-am' failed make[2]: *** [check-am] Error 2 make[2]: Leaving directory '/home/james/Downloads/autoconf-2.69/tests' Makefile:357: recipe for target 'check-recursive' failed make[1]: *** [check-recursive] Error 1 make[1]: Leaving directory '/home/james/Downloads/autoconf-2.69' Makefile:665: recipe for target 'check' failed make: *** [check] Error 2 I then found this section in testsuit.log: ## Detailed failed tests. ## ## ---------------------- ## # -*- compilation -*- 503. autoscan.at:20: testing autoscan ... ./autoscan.at:44: autoscan --- /dev/null 2017-04-30 14:32:24.816000000 -0500 +++ /home/james/Downloads/autoconf-2.69/tests/testsuite.dir/at-groups/503/stderr 2017-04-30 15:44:21.404662024 -0500 @@ -0,0 +1 @@ +Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/\${ <-- HERE [^\}]*}/ at /home/james/Downloads/autoconf-2.69/bin/autoscan line 361. 503. autoscan.at:20: 503. autoscan (autoscan.at:20): FAILED (autoscan.at:44) I escaped the first brace as indicated, ran "make check" again, and it completed successfully.