* Make simply reported an undefined variable For me, it was treated as an assignment:
martind@stormy:~/tmp/jerome-2025-07-28$ cat Makefile CXX == g++ martind@stormy:~/tmp/jerome-2025-07-28$ make -p 2>&1 | grep ^CXX CXX = = g++ martind@stormy:~/tmp/jerome-2025-07-28$ ... so the variable being undefined seems like an additional puzzle. * `==` is encountered in a context that ... isn’t a conditional test? Make doesn't use == for conditional tests. https://www.gnu.org/software/make/manual/html_node/Setting.html ... suggests it does have, yie ai ai, four different assignment operators, though there's a fifth at: https://www.gnu.org/software/make/manual/html_node/Conditional-Assignment.html You could try adding a warning if unexpected punctuation is adjacent to the equals sign, but I bet it'd go off on some real makefiles that don't put spaces around the assignment operators. If you were to only fire off the warning when there's a space before the assignment, then maybe the false positives would be rare enough to be acceptable. ________________________________ From: bug-make-bounces+martin.dorey=hds....@gnu.org <bug-make-bounces+martin.dorey=hds....@gnu.org> on behalf of Jerome Saint-Martin <jerome.saint-mar...@outlook.fr> Sent: Monday, July 28, 2025 01:59 To: bug-make@gnu.org <bug-make@gnu.org> Subject: Suggestion : warining when using == instead of = in a Makefile variable assignation ***** EXTERNAL EMAIL ***** Hello GNU Make team, Recently, I spent quite some time debugging a Makefile issue, only to realize that I had mistakenly written `==` instead of `=` when assigning a variable (e.g., `CXX == g++` instead of `CXX = g++`). Make simply reported an undefined variable later on, which made the root cause harder to spot. This kind of mistake is easy to make, especially for C++ developers who are used to writing `==` in conditionals. In C++, compilers like GCC emit warnings such as “value computed is not used” when an expression like `x == y;` is written outside a conditional context. Would it be feasible for GNU Make to emit a warning when `==` is encountered in a context that looks like a variable assignment, but isn’t a conditional test? I believe this could help many users catch such typos early. Thanks for considering this suggestion, and thank you for your work on Make! Best regards, Jerome
