dblaikie added a comment.
Haven't reviewed the code in detail, but the idea seems sound. Is there any
prior art in other compilers you can draw data/experiences from? & having some
data from some reasonably sized codebases on false positive (how often the
correct thing is to suppress the warning, versus fixing the warning) would
probably be useful. I would guess it doesn't meet the on-by-default bar we
would prefer for Clang, but might still be OK.
================
Comment at: clang/docs/ReleaseNotes.rst:64-74
+ - ``-Wimplicit-widening-of-pointer-offset``:
+
+ .. code-block:: c++
+
+ char* ptr_add(char *base, int a, int b) {
+ return base + a * b; // expected-warning {{result of multiplication in
type 'int' is used as a pointer offset after an implicit widening conversion to
type 'ssize_t'}}
+ }
----------------
Does this only trigger when the `sizeof(char*) > sizeof(int)`? (judging by the
test coverage I think that's the case)
(ultimately, might be worth committing the two diagnostics separately - usual
sort of reasons, separation of concerns, etc)
================
Comment at:
clang/test/Sema/implicit-widening-of-pointer-offset-in-array-subscript-expression.c:24
+void t1(char *base, int a, int b) {
+ // FIXME: test `[a * b]base` pattern?
+}
----------------
Question is unclear - is there uncertainty about whether this should be tested?
Or is this a false negative case? In which case I'd probably include the test
showing no diagnostic and mention it could be fixed/improved?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D93822/new/
https://reviews.llvm.org/D93822
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