[libunwind] 221c5af - Fix a -Wbitwise-conditional-parentheses warning in _LIBUNWIND_ARM_EHABI libunwind builds

[Nico Weber via cfe-commits]

Author: Nico Weber
Date: 2020-02-03T14:17:50-05:00
New Revision: 221c5af4e4f4a504a4d1f352dd7b76d305e56a62

URL: https://github.com/llvm/llvm-project/commit/221c5af4e4f4a504a4d1f352dd7b76d305e56a62
DIFF: https://github.com/llvm/llvm-project/commit/221c5af4e4f4a504a4d1f352dd7b76d305e56a62.diff

LOG: Fix a -Wbitwise-conditional-parentheses warning in _LIBUNWIND_ARM_EHABI libunwind builds

```
src/UnwindCursor.hpp:1344:51: error: operator '?:' has lower precedence than '|';
    '|' will be evaluated first [-Werror,-Wbitwise-conditional-parentheses]
  _info.flags = isSingleWordEHT ? 1 : 0 | scope32 ? 0x2 : 0;  // Use enum?
                                      ~~~~~~~~~~~ ^
src/UnwindCursor.hpp:1344:51: note: place parentheses around the '|' expression
    to silence this warning
  _info.flags = isSingleWordEHT ? 1 : 0 | scope32 ? 0x2 : 0;  // Use enum?
                                                  ^
                                      (          )
src/UnwindCursor.hpp:1344:51: note: place parentheses around the '?:' expression
    to evaluate it first
  _info.flags = isSingleWordEHT ? 1 : 0 | scope32 ? 0x2 : 0;  // Use enum?
                                                  ^
                                          (                )
```

But `0 |` is a no-op for either of those two interpretations, so I think
what was meant here was

```
  _info.flags = (isSingleWordEHT ? 1 : 0) | (scope32 ? 0x2 : 0);  // Use enum?
```

Previously, if `isSingleWordEHT` was set, bit 2 would never be set. Now
it is. From what I can tell, the only thing that checks these bitmask is
ProcessDescriptors in Unwind-EHABI.cpp, and that only cares about bit 1,
so in practice this shouldn't have much of an effect.

Differential Revision: https://reviews.llvm.org/D73890

Added: 
    

Modified: 
    libunwind/src/UnwindCursor.hpp

Removed: 
    


################################################################################
diff  --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
index 31be8366d238..e7fb70cc5718 100644
--- a/libunwind/src/UnwindCursor.hpp
+++ b/libunwind/src/UnwindCursor.hpp
@@ -1353,7 +1353,8 @@ bool UnwindCursor<A, R>::getInfoFromEHABISection(
 
   // If the high bit is set, the exception handling table entry is inline inside
   // the index table entry on the second word (aka |indexDataAddr|). Otherwise,
-  // the table points at an offset in the exception handling table (section 5 EHABI).
+  // the table points at an offset in the exception handling table (section 5
+  // EHABI).
   pint_t exceptionTableAddr;
   uint32_t exceptionTableData;
   bool isSingleWordEHT;
@@ -1452,7 +1453,7 @@ bool UnwindCursor<A, R>::getInfoFromEHABISection(
   _info.unwind_info = exceptionTableAddr;
   _info.lsda = lsda;
   // flags is pr_cache.additional. See EHABI #7.2 for definition of bit 0.
-  _info.flags = isSingleWordEHT ? 1 : 0 | scope32 ? 0x2 : 0;  // Use enum?
+  _info.flags = (isSingleWordEHT ? 1 : 0) | (scope32 ? 0x2 : 0);  // Use enum?
 
   return true;
 }