[PATCH] D79895: Add a new warning to warn when passing uninitialized variables as const reference parameters to a function

[Zequan Wu via Phabricator via cfe-commits]

zequanwu marked an inline comment as done.
zequanwu added a comment.

In D79895#2042992 <https://reviews.llvm.org/D79895#2042992>, @xbolva00 wrote:

> Can you provide some compile time data with warning enabled/disabled?


I compiled the test case with warning enabled and disabled. Since it is controlled by `-Wuninitialzed`, it will diagnose when the flag is given.

  $ clang -ftime-report -fsyntax-only warn-uninitialized-const-reference.cpp
  ===-------------------------------------------------------------------------===
                            Clang front-end time report
  ===-------------------------------------------------------------------------===
    Total Execution Time: 0.0094 seconds (0.0094 wall clock)
  
     ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
     0.0091 (100.0%)   0.0003 (100.0%)   0.0094 (100.0%)   0.0094 (100.0%)  Clang front-end timer
     0.0091 (100.0%)   0.0003 (100.0%)   0.0094 (100.0%)   0.0094 (100.0%)  Total
  
  $ clang -ftime-report -Wuninitialized -fsyntax-only warn-uninitialized-const-reference.cpp
  ===-------------------------------------------------------------------------===
                            Clang front-end time report
  ===-------------------------------------------------------------------------===
    Total Execution Time: 0.0131 seconds (0.0131 wall clock)
  
     ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
     0.0046 (100.0%)   0.0086 (100.0%)   0.0131 (100.0%)   0.0131 (100.0%)  Clang front-end timer
     0.0046 (100.0%)   0.0086 (100.0%)   0.0131 (100.0%)   0.0131 (100.0%)  Total
  
  $ clang -ftime-report -Wuninitialized -Wno-uninitialized-const-reference -fsyntax-only warn-uninitialized-const-reference.cpp
  ===-------------------------------------------------------------------------===
                            Clang front-end time report
  ===-------------------------------------------------------------------------===
    Total Execution Time: 0.0109 seconds (0.0109 wall clock)
  
     ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
     0.0073 (100.0%)   0.0036 (100.0%)   0.0109 (100.0%)   0.0109 (100.0%)  Clang front-end timer
     0.0073 (100.0%)   0.0036 (100.0%)   0.0109 (100.0%)   0.0109 (100.0%)  Total



================
Comment at: clang/test/SemaCXX/warn-uninitialized-const-reference.cpp:23
+    int k = const_use(k); // expected-warning {{variable 'k' is uninitialized when used within its own initialization}}
+    A a2 = const_use_A(a2); // expected-warning {{variable 'a2' is uninitialized when used within its own initialization}}
+    A a3(const_ref_use_A(a3)); // expected-warning {{variable 'a3' is uninitialized when passes as a const reference parameter here}}
----------------
zequanwu wrote:
> aeubanks wrote:
> > For my knowledge, is this to make sure that this other warning takes precedence over the one introduced in this change? If it is, a comment would be nice.
> No, original behavior of `-Wuninitialized` for line 24 is silence. Now the new warning will be emitted because it is const use of uninitialized variable.
I meant "const reference use". It was typo.


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https://reviews.llvm.org/D79895