[llvm-bugs] [Bug 36505] New: Clang-tidy: expression with calls to a non-pure function is considered as always-true

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36505

            Bug ID: 36505
           Summary: Clang-tidy: expression with calls to a non-pure
                    function is considered as always-true
           Product: clang
           Version: 5.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Static Analyzer
          Assignee: dcoughlin at apple.com
          Reporter: pavel.kryukov at phystech.edu
                CC: llvm-bugs at lists.llvm.org

Created attachment 19951
  --> https://bugs.llvm.org/attachment.cgi?id=19951&action=edit
Example of always-true false positive with calls to a non-pure function

Clang-Tidy produces a false positive warning about always-true expression
(misc-redundant-expression check) if expression contains consequent calls to a
non-pure function which have different return values:

$> clang-tidy -checks='*' ldfile.c -- -Wall
15 warnings generated.
./ldfile.c:11:32: warning: logical expression is always true
[misc-redundant-expression]
    if ((token = yylex()) != 1 || (token = yylex()) != 2) {
                               ^
Suppressed 14 warnings (14 in non-user code).

$> clang ldfile.c -Wall -Wextra && ./a.out
false

The code is taken from GNU Binutils (/ld/ldfile.c) source file.

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