[PATCH] D123009: [Sema] Enum conversion warning when one signed and other unsigned.

[Micah Weston via Phabricator via cfe-commits]

red1bluelost created this revision.
red1bluelost added reviewers: rsmith, lebedev.ri, aaron.ballman.
Herald added a project: All.
red1bluelost requested review of this revision.
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Ensures an -Wenum-conversion warning happens when one of the enums is
signed and the other is unsigned. Also adds a test file to verify these
warnings.

This warning would not happen since the -Wsign-conversion would make a
diagnostic then return, never allowing the -Wenum-conversion checks.

For example:

  C
  enum PE { P = -1 };
  enum NE { N };
  enum NE conv(enum PE E) { return E; }

Before this would only create a diagnostic with -Wsign-conversion and never on 
-Wenum-conversion. Now it will create a diagnostic for both -Wsign-conversion 
and -Wenum-conversion.

I could change it to just warn on -Wenum-conversion as that was what I initially
did. Seeing PR35200 (or GitHub Issue 316268), I let both diagnostics check so that
the sign conversion could generate a warning.

This was tested with `check-clang` and all tests passed along with the new test
file.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123009

Files:
  clang/lib/Sema/SemaChecking.cpp
  clang/test/Sema/enum-enum-conversion.c


Index: clang/test/Sema/enum-enum-conversion.c
===================================================================
--- /dev/null
+++ clang/test/Sema/enum-enum-conversion.c
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -verify -Wenum-conversion -DENUM_CONV %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -verify -Wconversion %s
+
+enum NE1 { N1 = -1 };
+enum NE2 { N2 = -2 };
+enum PE1 { P1 };
+enum PE2 { P2 };
+
+enum PE2 f1(enum PE1 E) {
+#ifdef ENUM_CONV
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum PE1' to different enumeration type 'enum PE2'}}
+#else
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum PE1' to different enumeration type 'enum PE2'}}
+#endif
+}
+
+enum NE1 f2(enum PE1 E) {
+#ifdef ENUM_CONV
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum PE1' to different enumeration type 'enum NE1'}}
+#else
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum PE1' to different enumeration type 'enum NE1'}} expected-warning {{implicit conversion changes signedness: 'enum PE1' to 'enum NE1'}}
+#endif
+}
+
+enum PE1 f3(enum NE1 E) {
+#ifdef ENUM_CONV
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum NE1' to different enumeration type 'enum PE1'}}
+#else
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum NE1' to different enumeration type 'enum PE1'}} expected-warning {{implicit conversion changes signedness: 'enum NE1' to 'enum PE1'}}
+#endif
+}
+
+enum NE2 f4(enum NE1 E) {
+#ifdef ENUM_CONV
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum NE1' to different enumeration type 'enum NE2'}}
+#else
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum NE1' to different enumeration type 'enum NE2'}}
+#endif
+}
\ No newline at end of file
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -13552,7 +13552,9 @@
       *ICContext = true;
     }
 
-    return DiagnoseImpCast(S, E, T, CC, DiagID);
+    DiagnoseImpCast(S, E, T, CC, DiagID);
+    if (!isa<EnumType>(Target) || !isa<EnumType>(Source))
+      return;
   }
 
   // Diagnose conversions between different enumeration types.


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