https://llvm.org/bugs/show_bug.cgi?id=25552
Bug ID: 25552
Summary: extend -fwrapv to apply to left shifts
Product: clang
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: bonz...@gnu.org
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
If you pass clang -fwrapv then this causes -fsanitize=undefined to no longer
complain about signed integer overflows from addition. However the sanitizer
will still complain about left shifts of negative values.
-fwrapv should apply also to shifts. In addition -fwrapv in clang should
suppress -Wshift-negative-value.
(The GCC manuals only mention -fwrapv to affect add/sub/mult because GCC
currently _never_ treats signed left shifts as having undefined behavior. GCC
documentation however says very clearly, under -fstrict-overflow, that "Using
'-fwrapv' means that integer signed overflow is fully defined: it wraps").
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