Handle the obvious case for diagnosing redeclarations of extern "C" functions.

Fixes PR7859.

llvm-svn: 110906

2 files changed, 16 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 339a79384c2..047a5d9ba58 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -573,6 +573,11 @@ Sema::CheckOverload(Scope *S, FunctionDecl *New, const LookupResult &Old,
 
 bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
                       bool UseUsingDeclRules) {
+  // If both of the functions are extern "C", then they are not
+  // overloads.
+  if (Old->isExternC() && New->isExternC())
+    return false;
+
   FunctionTemplateDecl *OldTemplate = Old->getDescribedFunctionTemplate();
   FunctionTemplateDecl *NewTemplate = New->getDescribedFunctionTemplate();
 
diff --git a/clang/test/SemaCXX/linkage-spec.cpp b/clang/test/SemaCXX/linkage-spec.cpp
index 0d1c166dcb3..fdb642c78fc 100644
--- a/clang/test/SemaCXX/linkage-spec.cpp
+++ b/clang/test/SemaCXX/linkage-spec.cpp
@@ -57,3 +57,14 @@ extern "C"
 
 // PR6991
 extern "C" typedef int (*PutcFunc_t)(int);
+
+
+// PR7859
+extern "C" void pr7859_a(int) {} // expected-note {{previous definition}}
+extern "C" void pr7859_a(int) {} // expected-error {{redefinition}}
+
+extern "C" void pr7859_b() {} // expected-note {{previous definition}}
+extern "C" void pr7859_b(int) {} // expected-error {{conflicting}}
+
+extern "C" void pr7859_c(short) {} // expected-note {{previous definition}}
+extern "C" void pr7859_c(int) {} // expected-error {{conflicting}}