[Sema] -Wzero-as-null-pointer-constant: don't warn for system macros other than NULL.
Summary:
The warning was initially introduced in D32914 by @thakis,
and the concerns were raised there, and later in rL302247
and PR33771.
I do believe that it makes sense to relax the diagnostic
e.g. in this case, when the expression originates from the
system header, which can not be modified. This prevents
adoption for the diagnostic for codebases which use pthreads
(`PTHREAD_MUTEX_INITIALIZER`), gtest, etc.
As @malcolm.parsons suggests, it *may* make sense to also
not warn for the template types, but it is not obvious to
me how to do that in here.
Though, it still makes sense to complain about `NULL` macro.
While there, add more tests.
Reviewers: dblaikie, thakis, rsmith, rjmccall, aaron.ballman
Reviewed By: thakis
Subscribers: Rakete1111, hans, cfe-commits, thakis, malcolm.parsons
Tags: #clang
Differential Revision: https://reviews.llvm.org/D38954
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@316662 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 5f17d5ca46b48156b96f81e7c32d381a0ca65b41)
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 4af76a7..faf7f40 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -65,6 +65,9 @@
default. It warns about unguarded uses of APIs only when they were introduced
in or after macOS 10.13, iOS 11, tvOS 11 or watchOS 4.
+- ``-Wzero-as-null-pointer-constant`` was adjusted not to warn on null pointer
+ constants that originate from system macros, except ``NULL`` macro.
+
- The ``-Wdocumentation`` warning now allows the use of ``\param`` and
``\returns`` documentation directives in the documentation comments for
declarations with a function or a block pointer type.
diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index 6417b44..7f627a3 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -389,12 +389,24 @@
}
void Sema::diagnoseZeroToNullptrConversion(CastKind Kind, const Expr* E) {
+ if (Diags.isIgnored(diag::warn_zero_as_null_pointer_constant,
+ E->getLocStart()))
+ return;
+ // nullptr only exists from C++11 on, so don't warn on its absence earlier.
+ if (!getLangOpts().CPlusPlus11)
+ return;
+
if (Kind != CK_NullToPointer && Kind != CK_NullToMemberPointer)
return;
if (E->IgnoreParenImpCasts()->getType()->isNullPtrType())
return;
- // nullptr only exists from C++11 on, so don't warn on its absence earlier.
- if (!getLangOpts().CPlusPlus11)
+
+ // If it is a macro from system header, and if the macro name is not "NULL",
+ // do not warn.
+ SourceLocation MaybeMacroLoc = E->getLocStart();
+ if (Diags.getSuppressSystemWarnings() &&
+ SourceMgr.isInSystemMacro(MaybeMacroLoc) &&
+ !findMacroSpelling(MaybeMacroLoc, "NULL"))
return;
Diag(E->getLocStart(), diag::warn_zero_as_null_pointer_constant)
diff --git a/test/SemaCXX/Inputs/warn-zero-nullptr.h b/test/SemaCXX/Inputs/warn-zero-nullptr.h
new file mode 100644
index 0000000..9b86c4b
--- /dev/null
+++ b/test/SemaCXX/Inputs/warn-zero-nullptr.h
@@ -0,0 +1,3 @@
+#define NULL (0)
+#define SYSTEM_MACRO (0)
+#define OTHER_SYSTEM_MACRO (NULL)
diff --git a/test/SemaCXX/warn-zero-nullptr.cpp b/test/SemaCXX/warn-zero-nullptr.cpp
index 7228040..45f05fa 100644
--- a/test/SemaCXX/warn-zero-nullptr.cpp
+++ b/test/SemaCXX/warn-zero-nullptr.cpp
@@ -1,4 +1,10 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s -Wzero-as-null-pointer-constant -std=c++11
+// RUN: %clang_cc1 -fsyntax-only -verify %s -isystem %S/Inputs -Wzero-as-null-pointer-constant -std=c++11
+// RUN: %clang_cc1 -fsyntax-only -verify %s -isystem %S/Inputs -DSYSTEM_WARNINGS -Wzero-as-null-pointer-constant -Wsystem-headers -std=c++11
+
+#include <warn-zero-nullptr.h>
+
+#define MACRO (0)
+#define MCRO(x) (x)
struct S {};
@@ -15,8 +21,12 @@
void (*fp2)() = __null; // expected-warning{{zero as null pointer constant}}
int (S::*mp2) = __null; // expected-warning{{zero as null pointer constant}}
-void f0(void* v = 0); // expected-warning{{zero as null pointer constant}}
-void f1(void* v);
+void f0(void* v = MACRO); // expected-warning{{zero as null pointer constant}}
+void f1(void* v = NULL); // expected-warning{{zero as null pointer constant}}
+void f2(void* v = MCRO(0)); // expected-warning{{zero as null pointer constant}}
+void f3(void* v = MCRO(NULL)); // expected-warning{{zero as null pointer constant}}
+void f4(void* v = 0); // expected-warning{{zero as null pointer constant}}
+void f5(void* v);
void g() {
f1(0); // expected-warning{{zero as null pointer constant}}
@@ -32,3 +42,51 @@
void func() { if (nullptr == A()) {} }
void func2() { if ((nullptr) == A()) {} }
}
+
+template <typename T> void TmplFunc0(T var) {}
+void Func0Test() {
+ TmplFunc0<int>(0);
+ TmplFunc0<int*>(0); // expected-warning {{zero as null pointer constant}}
+ TmplFunc0<void*>(0); // expected-warning {{zero as null pointer constant}}
+}
+
+// FIXME: this one probably should not warn.
+template <typename T> void TmplFunc1(int a, T default_value = 0) {} // expected-warning{{zero as null pointer constant}} expected-warning{{zero as null pointer constant}}
+void FuncTest() {
+ TmplFunc1<int>(0);
+ TmplFunc1<int*>(0); // expected-note {{in instantiation of default function argument expression for 'TmplFunc1<int *>' required here}}
+ TmplFunc1<void*>(0); // expected-note {{in instantiation of default function argument expression for 'TmplFunc1<void *>' required here}}
+}
+
+template<typename T>
+class TemplateClass0 {
+ public:
+ explicit TemplateClass0(T var) {}
+};
+void TemplateClass0Test() {
+ TemplateClass0<int> a(0);
+ TemplateClass0<int*> b(0); // expected-warning {{zero as null pointer constant}}
+ TemplateClass0<void*> c(0); // expected-warning {{zero as null pointer constant}}
+}
+
+template<typename T>
+class TemplateClass1 {
+ public:
+// FIXME: this one should *NOT* warn.
+ explicit TemplateClass1(int a, T default_value = 0) {} // expected-warning{{zero as null pointer constant}} expected-warning{{zero as null pointer constant}}
+};
+void IgnoreSubstTemplateType1() {
+ TemplateClass1<int> a(1);
+ TemplateClass1<int*> b(1); // expected-note {{in instantiation of default function argument expression for 'TemplateClass1<int *>' required here}}
+ TemplateClass1<void*> c(1); // expected-note {{in instantiation of default function argument expression for 'TemplateClass1<void *>' required here}}
+}
+
+#ifndef SYSTEM_WARNINGS
+// Do not warn on *any* other macros from system headers, even if they
+// expand to/their expansion contains NULL.
+void* sys_init = SYSTEM_MACRO;
+void* sys_init2 = OTHER_SYSTEM_MACRO;
+#else
+void* sys_init = SYSTEM_MACRO; // expected-warning {{zero as null pointer constant}}
+void* sys_init2 = OTHER_SYSTEM_MACRO; // expected-warning {{zero as null pointer constant}}
+#endif
