GitHub CI pipeline: early-warning cells back to Boost 1.91.0, with Boost.Regex no longer excluded in conanfile.py: the conan-center boost/1.91.0 recipe built boost_regex anyway (some module we build now needs it) and then failed its own library-consistency check ("built, but were not used in any boost module: boost_regex"); same class of problem, and same disposition, as the 1.87 context case already noted in conanfile.py.

Author: ygoldfeld

.github/workflows/main.yml

@@ -274,13 +274,14 @@ jobs:
         # `newest` = "early-warning" runs with newest conan-center versions of key dependencies).  Explained in
         # Flow-IPC workflow counterpart.  For Flow the only such dependency is Boost.  Bump the `newest` version
         # when conan-center gets a newer one.  (TODO: Some kind of reminder system to inform maintainer(s).)
+        # (1.91.0 required un-excluding Boost.Regex in conanfile.py; see the comment there.)
         deps:
           - id: floor
             name-suffix: ''
           - id: newest
             name-suffix: -deps-newest
             conan-profile-replace-requires: |
-              boost/*: boost/1.90.0
+              boost/*: boost/1.91.0
 
         # Remove certain values from the 4D matrix so far.
         # The overall strategy is outlined in a large-ish comment above (or in Flow-IPC pipeline file;

conanfile.py

@@ -78,7 +78,13 @@ def configure(self):
             self.options["boost"].without_mpi = True
             self.options["boost"].without_nowide = True
             self.options["boost"].without_python = True
-            self.options["boost"].without_regex = True
+            # TODO: The next line is commented out, like `without_context` above, for the same reason: with Boost
+            # 1.91.0 (the early-warning pipeline cells) the same ConanException fires -- this time
+            # `{'boost_regex'}` -- even though b2 itself reports `regex: not building`; so apparently some module
+            # we *do* build now requires `regex` to itself build, and the recipe's bookkeeping does not know it.
+            # Same disposition: this gets rid of the problem; look into it sometime.  (Boost.Regex is header-only
+            # since 1.76 for our purposes; the built library is unused by us either way.)
+            # self.options["boost"].without_regex = True
             self.options["boost"].without_serialization = True
             self.options["boost"].without_stacktrace = True
             self.options["boost"].without_test = True