[llvm-bugs] [Bug 36861] New: ObjC: negating 'self' should issue warning. E.g: typo in !self->value causes hard-to-catch problems

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36861

            Bug ID: 36861
           Summary: ObjC: negating 'self' should issue warning. E.g: typo
                    in !self->value causes hard-to-catch problems
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: wkoszek at gmail.com
                CC: llvm-bugs at lists.llvm.org

Hello.

## Environment:

       My Xcode: Version 9.2 (9C40b)
       My clang version is below.

## Bug:

I've found this in one of our source files:

        if (!self->writeCount || !self-readCount) {
                NSLog(@"bleh");
        }

In ObjC source code, it'd be great to treat 'self' a little more special.
Otherwise it's very easy to hit something like the thing above.

(note: there's no ->readCount; instead it's -readCount). `self` here is
negated, which makes the whole expression make sense. However it's not what the
person wanted. I know it's hard (as it's valid to test for if (!self), but
maybe there's some compiler magician who could suggest wrapping
"self-readCount" in braces, in which case we'd get:

        weirdbug.m:30:33: error: arithmetic on pointer to interface
'SampleStream', which is not a constant size for this architecture and platform

## To replicate

       git clone https://github.com/wkoszek/edu_objc.git
       cd edu_objc
       make

The file is weirdbug.m.

=== my clang version ===

$ clang --version
Apple LLVM version 9.0.0 (clang-900.0.39.2)
Target: x86_64-apple-darwin17.4.0
Thread model: posix
InstalledDir:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20180321/201b74a7/attachment.html>