[clang] 34b9b1e - Disable -Wmissing-prototypes for internal linkage functions that aren't explicitly marked "static"

[David Blaikie via cfe-commits]

Author: David Blaikie
Date: 2022-03-25T23:53:19Z
New Revision: 34b9b1ea4874b109b998d59a837f81f2f730001c

URL: https://github.com/llvm/llvm-project/commit/34b9b1ea4874b109b998d59a837f81f2f730001c
DIFF: https://github.com/llvm/llvm-project/commit/34b9b1ea4874b109b998d59a837f81f2f730001c.diff

LOG: Disable -Wmissing-prototypes for internal linkage functions that aren't explicitly marked "static"

Some functions can end up non-externally visible despite not being
declared "static" or in an unnamed namespace in C++ - such as by having
parameters that are of non-external types.

Such functions aren't mistakenly intended to be defining some function
that needs a declaration. They could be maybe more legible (except for
the operator new example) with an explicit static, but that's a
stylistic thing outside what should be addressed by a warning.

This reapplies 275c56226d7fbd6a4d554807374f78d323aa0c1c - once we figure
out what to do about the change in behavior for -Wnon-c-typedef-for-linkage
(this reverts the revert commit 85ee1d3ca1d06b6bd3477515b8d0c72c8df7c069)

Differential Revision: https://reviews.llvm.org/D121328

Added: 
    

Modified: 
    clang/lib/Sema/SemaDecl.cpp
    clang/test/SemaCXX/anonymous-struct.cpp
    clang/test/SemaCXX/warn-missing-prototypes.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 5c262063a6aef..4051ab29fb26f 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -14233,6 +14233,11 @@ ShouldWarnAboutMissingPrototype(const FunctionDecl *FD,
   if (FD->isDeleted())
     return false;
 
+  // Don't warn on implicitly local functions (such as having local-typed
+  // parameters).
+  if (!FD->isExternallyVisible())
+    return false;
+
   for (const FunctionDecl *Prev = FD->getPreviousDecl();
        Prev; Prev = Prev->getPreviousDecl()) {
     // Ignore any declarations that occur in function or method

diff  --git a/clang/test/SemaCXX/anonymous-struct.cpp b/clang/test/SemaCXX/anonymous-struct.cpp
index 0a5395e15780b..7cf05ee3c49ae 100644
--- a/clang/test/SemaCXX/anonymous-struct.cpp
+++ b/clang/test/SemaCXX/anonymous-struct.cpp
@@ -183,3 +183,9 @@ namespace BuiltinName {
     void memcpy(); // expected-note {{due to this member}}
   } A; // expected-note {{given name 'A' for linkage purposes by this typedef}}
 }
+namespace inline_defined_static_member {
+typedef struct { // expected-warning {{anonymous non-C-compatible type}}
+  static void f() { // expected-note {{due to this member}}
+  }
+} A; // expected-note {{given name 'A' for linkage purposes by this typedef}}
+}

diff  --git a/clang/test/SemaCXX/warn-missing-prototypes.cpp b/clang/test/SemaCXX/warn-missing-prototypes.cpp
index e8637e5a90eab..2880514ee02b7 100644
--- a/clang/test/SemaCXX/warn-missing-prototypes.cpp
+++ b/clang/test/SemaCXX/warn-missing-prototypes.cpp
@@ -44,3 +44,16 @@ void j() = delete;
 extern void k() {} // expected-warning {{no previous prototype for function 'k'}}
 // expected-note at -1{{declare 'static' if the function is not intended to be used outside of this translation unit}}
 // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-2]]:{{.*}}-[[@LINE-2]]:{{.*}}}:"{{.*}}"
+
+namespace {
+struct anon { };
+}
+
+// No warning because this has internal linkage despite not being declared
+// explicitly 'static', owing to the internal linkage parameter.
+void l(anon) {
+}
+
+void *operator new(decltype(sizeof(3)) size, const anon &) throw() {
+  return nullptr;
+}