[llvm-bugs] [Bug 46991] New: False positives in core.NullDereference on non_odr_use_constant DeclRefExpr to non-capture

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46991

            Bug ID: 46991
           Summary: False positives in core.NullDereference on
                    non_odr_use_constant DeclRefExpr to non-capture
           Product: clang
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Static Analyzer
          Assignee: dcoughlin at apple.com
          Reporter: aaronpuchert at alice-dsl.net
                CC: dcoughlin at apple.com, llvm-bugs at lists.llvm.org

On the following code:

void foo(int v);
constexpr int VAL = 1;
void bar()
{
    const int& val = VAL;
    []() {
        foo(val);
    }();
}

the static analyzer warns

<source>:7:13: warning: Dereference of undefined pointer value
[core.NullDereference]
        foo(val);
            ^
<source>:6:5: note: Uninitialized value stored to 'val'
    []() {
    ^~~~~~
<source>:6:5: note: Calling 'operator()'
    []() {
    ^~~~~~
<source>:7:13: note: Dereference of undefined pointer value
        foo(val);
            ^~~

I think that's wrong, val has an initializer expression. Note that the
DeclRefExpr referring to val is marked as non_odr_use_constant, and val doesn't
need to be captured. Adding an explicit capture fixes the Static Analyzer issue
but raises a regular Clang warning:

<source>:6:6: warning: lambda capture 'val' is not required to be captured for
this use [-Wunused-lambda-capture]
    [val]() {
     ^~~

or

<source>:6:7: warning: lambda capture 'val' is not required to be captured for
this use [-Wunused-lambda-capture]
    [&val]() {
     ~^~~

Using a capture-default expression, i.e. [=] or [&], does not fix the issue.

-- 
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/20200804/5e93d940/attachment.html>