r264132 - [Sema] Allow implicit conversions of &overloaded_fn in C.
George Burgess IV via cfe-commits
cfe-commits at lists.llvm.org
Tue Mar 22 19:33:58 PDT 2016
Author: gbiv
Date: Tue Mar 22 21:33:58 2016
New Revision: 264132
URL: http://llvm.org/viewvc/llvm-project?rev=264132&view=rev
Log:
[Sema] Allow implicit conversions of &overloaded_fn in C.
Also includes a minor ``enable_if`` docs update.
Currently, our address-of overload machinery will only allow implicit
conversions of overloaded functions to void* in C. For example:
```
void f(int) __attribute__((overloadable));
void f(double) __attribute__((overloadable, enable_if(0, "")));
void *fp = f; // OK. This is C and the target is void*.
void (*fp2)(void) = f; // Error. This is C, but the target isn't void*.
```
This patch makes the assignment of `fp2` select the `f(int)` overload,
rather than emitting an error (N.B. you'll still get a warning about the
`fp2` assignment if you use -Wincompatible-pointer-types).
Differential Revision: http://reviews.llvm.org/D13704
Modified:
cfe/trunk/include/clang/Basic/AttrDocs.td
cfe/trunk/lib/Sema/SemaOverload.cpp
cfe/trunk/test/CodeGen/overloadable.c
cfe/trunk/test/Sema/overloadable.c
cfe/trunk/test/Sema/pass-object-size.c
Modified: cfe/trunk/include/clang/Basic/AttrDocs.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/AttrDocs.td?rev=264132&r1=264131&r2=264132&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/AttrDocs.td (original)
+++ cfe/trunk/include/clang/Basic/AttrDocs.td Tue Mar 22 21:33:58 2016
@@ -260,6 +260,29 @@ only a single candidate. In a call to g(
not ODR-equivalent.
Query for this feature with ``__has_attribute(enable_if)``.
+
+Note that functions with one or more ``enable_if`` attributes may not have
+their address taken, unless all of the conditions specified by said
+``enable_if`` are constants that evaluate to ``true``. For example:
+
+.. code-block:: c
+
+ const int TrueConstant = 1;
+ const int FalseConstant = 0;
+ int f(int a) __attribute__((enable_if(a > 0, "")));
+ int g(int a) __attribute__((enable_if(a == 0 || a != 0, "")));
+ int h(int a) __attribute__((enable_if(1, "")));
+ int i(int a) __attribute__((enable_if(TrueConstant, "")));
+ int j(int a) __attribute__((enable_if(FalseConstant, "")));
+
+ void fn() {
+ int (*ptr)(int);
+ ptr = &f; // error: 'a > 0' is not always true
+ ptr = &g; // error: 'a == 0 || a != 0' is not a truthy constant
+ ptr = &h; // OK: 1 is a truthy constant
+ ptr = &i; // OK: 'TrueConstant' is a truthy constant
+ ptr = &j; // error: 'FalseConstant' is a constant, but not truthy
+ }
}];
}
Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=264132&r1=264131&r2=264132&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
+++ cfe/trunk/lib/Sema/SemaOverload.cpp Tue Mar 22 21:33:58 2016
@@ -8488,7 +8488,7 @@ Sema::AddArgumentDependentLookupCandidat
// Cand1's first N enable_if attributes have precisely the same conditions as
// Cand2's first N enable_if attributes (where N = the number of enable_if
// attributes on Cand2), and Cand1 has more than N enable_if attributes.
-static bool hasBetterEnableIfAttrs(Sema &S, const FunctionDecl *Cand1,
+static bool hasBetterEnableIfAttrs(const Sema &S, const FunctionDecl *Cand1,
const FunctionDecl *Cand2) {
// FIXME: The next several lines are just
@@ -10299,13 +10299,25 @@ public:
bool hasComplained() const { return HasComplained; }
private:
- // Is A considered a better overload candidate for the desired type than B?
+ bool candidateHasExactlyCorrectType(const FunctionDecl *FD) {
+ QualType Discard;
+ return Context.hasSameUnqualifiedType(TargetFunctionType, FD->getType()) ||
+ S.IsNoReturnConversion(FD->getType(), TargetFunctionType, Discard);
+ }
+
+ /// \return true if A is considered a better overload candidate for the
+ /// desired type than B.
bool isBetterCandidate(const FunctionDecl *A, const FunctionDecl *B) {
- return hasBetterEnableIfAttrs(S, A, B);
+ // If A doesn't have exactly the correct type, we don't want to classify it
+ // as "better" than anything else. This way, the user is required to
+ // disambiguate for us if there are multiple candidates and no exact match.
+ return candidateHasExactlyCorrectType(A) &&
+ (!candidateHasExactlyCorrectType(B) ||
+ hasBetterEnableIfAttrs(S, A, B));
}
- // Returns true if we've eliminated any (read: all but one) candidates, false
- // otherwise.
+ /// \return true if we were able to eliminate all but one overload candidate,
+ /// false otherwise.
bool eliminiateSuboptimalOverloadCandidates() {
// Same algorithm as overload resolution -- one pass to pick the "best",
// another pass to be sure that nothing is better than the best.
@@ -10418,12 +10430,9 @@ private:
if (!S.checkAddressOfFunctionIsAvailable(FunDecl))
return false;
- QualType ResultTy;
- if (Context.hasSameUnqualifiedType(TargetFunctionType,
- FunDecl->getType()) ||
- S.IsNoReturnConversion(FunDecl->getType(), TargetFunctionType,
- ResultTy) ||
- (!S.getLangOpts().CPlusPlus && TargetType->isVoidPointerType())) {
+ // If we're in C, we need to support types that aren't exactly identical.
+ if (!S.getLangOpts().CPlusPlus ||
+ candidateHasExactlyCorrectType(FunDecl)) {
Matches.push_back(std::make_pair(
CurAccessFunPair, cast<FunctionDecl>(FunDecl->getCanonicalDecl())));
FoundNonTemplateFunction = true;
Modified: cfe/trunk/test/CodeGen/overloadable.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/overloadable.c?rev=264132&r1=264131&r2=264132&view=diff
==============================================================================
--- cfe/trunk/test/CodeGen/overloadable.c (original)
+++ cfe/trunk/test/CodeGen/overloadable.c Tue Mar 22 21:33:58 2016
@@ -29,3 +29,33 @@ int main() {
cdv = f(cdv);
vv = f(vv);
}
+
+// Ensuring that we pick the correct function for taking the address of an
+// overload when conversions are involved.
+
+void addrof_many(int *a) __attribute__((overloadable, enable_if(0, "")));
+void addrof_many(void *a) __attribute__((overloadable));
+void addrof_many(char *a) __attribute__((overloadable));
+
+void addrof_single(int *a) __attribute__((overloadable, enable_if(0, "")));
+void addrof_single(char *a) __attribute__((overloadable, enable_if(0, "")));
+void addrof_single(char *a) __attribute__((overloadable));
+
+// CHECK-LABEL: define void @foo
+void foo() {
+ // CHECK: store void (i8*)* @_Z11addrof_manyPc
+ void (*p1)(char *) = &addrof_many;
+ // CHECK: store void (i8*)* @_Z11addrof_manyPv
+ void (*p2)(void *) = &addrof_many;
+ // CHECK: void (i8*)* @_Z11addrof_manyPc
+ void *vp1 = (void (*)(char *)) & addrof_many;
+ // CHECK: void (i8*)* @_Z11addrof_manyPv
+ void *vp2 = (void (*)(void *)) & addrof_many;
+
+ // CHECK: store void (i8*)* @_Z13addrof_singlePc
+ void (*p3)(char *) = &addrof_single;
+ // CHECK: @_Z13addrof_singlePc
+ void (*p4)(int *) = &addrof_single;
+ // CHECK: @_Z13addrof_singlePc
+ void *vp3 = &addrof_single;
+}
Modified: cfe/trunk/test/Sema/overloadable.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/overloadable.c?rev=264132&r1=264131&r2=264132&view=diff
==============================================================================
--- cfe/trunk/test/Sema/overloadable.c (original)
+++ cfe/trunk/test/Sema/overloadable.c Tue Mar 22 21:33:58 2016
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -verify %s -Wincompatible-pointer-types
int var __attribute__((overloadable)); // expected-error{{'overloadable' attribute only applies to functions}}
void params(void) __attribute__((overloadable(12))); // expected-error {{'overloadable' attribute takes no arguments}}
@@ -99,3 +99,26 @@ void conversions() {
unsigned char *c;
multi_type(c);
}
+
+// Ensure that we allow C-specific type conversions in C
+void fn_type_conversions() {
+ void foo(void *c) __attribute__((overloadable));
+ void foo(char *c) __attribute__((overloadable));
+ void (*ptr1)(void *) = &foo;
+ void (*ptr2)(char *) = &foo;
+ void (*ambiguous)(int *) = &foo; // expected-error{{initializing 'void (*)(int *)' with an expression of incompatible type '<overloaded function type>'}} expected-note at 105{{candidate function}} expected-note at 106{{candidate function}}
+ void *vp_ambiguous = &foo; // expected-error{{initializing 'void *' with an expression of incompatible type '<overloaded function type>'}} expected-note at 105{{candidate function}} expected-note at 106{{candidate function}}
+
+ void (*specific1)(int *) = (void (*)(void *))&foo; // expected-warning{{incompatible pointer types initializing 'void (*)(int *)' with an expression of type 'void (*)(void *)'}}
+ void *specific2 = (void (*)(void *))&foo;
+
+ void disabled(void *c) __attribute__((overloadable, enable_if(0, "")));
+ void disabled(int *c) __attribute__((overloadable, enable_if(c, "")));
+ void disabled(char *c) __attribute__((overloadable, enable_if(1, "The function name lies.")));
+ // To be clear, these should all point to the last overload of 'disabled'
+ void (*dptr1)(char *c) = &disabled;
+ void (*dptr2)(void *c) = &disabled; // expected-warning{{incompatible pointer types initializing 'void (*)(void *)' with an expression of type '<overloaded function type>'}} expected-note at 115{{candidate function made ineligible by enable_if}} expected-note at 116{{candidate function made ineligible by enable_if}} expected-note at 117{{candidate function has type mismatch at 1st parameter (expected 'void *' but has 'char *')}}
+ void (*dptr3)(int *c) = &disabled; // expected-warning{{incompatible pointer types initializing 'void (*)(int *)' with an expression of type '<overloaded function type>'}} expected-note at 115{{candidate function made ineligible by enable_if}} expected-note at 116{{candidate function made ineligible by enable_if}} expected-note at 117{{candidate function has type mismatch at 1st parameter (expected 'int *' but has 'char *')}}
+
+ void *specific_disabled = &disabled;
+}
Modified: cfe/trunk/test/Sema/pass-object-size.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/pass-object-size.c?rev=264132&r1=264131&r2=264132&view=diff
==============================================================================
--- cfe/trunk/test/Sema/pass-object-size.c (original)
+++ cfe/trunk/test/Sema/pass-object-size.c Tue Mar 22 21:33:58 2016
@@ -38,8 +38,8 @@ void FunctionPtrs() {
void (*p)(void *) = NotOverloaded; //expected-error{{cannot take address of function 'NotOverloaded' because parameter 1 has pass_object_size attribute}}
void (*p2)(void *) = &NotOverloaded; //expected-error{{cannot take address of function 'NotOverloaded' because parameter 1 has pass_object_size attribute}}
- void (*p3)(void *) = IsOverloaded; //expected-error{{initializing 'void (*)(void *)' with an expression of incompatible type '<overloaded function type>'}} expected-note at -6{{candidate address cannot be taken because parameter 1 has pass_object_size attribute}} expected-note at -5{{type mismatch}}
- void (*p4)(void *) = &IsOverloaded; //expected-error{{initializing 'void (*)(void *)' with an expression of incompatible type '<overloaded function type>'}} expected-note at -7{{candidate address cannot be taken because parameter 1 has pass_object_size attribute}} expected-note at -6{{type mismatch}}
+ void (*p3)(void *) = IsOverloaded; //expected-warning{{incompatible pointer types initializing 'void (*)(void *)' with an expression of type '<overloaded function type>'}} expected-note at -6{{candidate address cannot be taken because parameter 1 has pass_object_size attribute}} expected-note at -5{{type mismatch}}
+ void (*p4)(void *) = &IsOverloaded; //expected-warning{{incompatible pointer types initializing 'void (*)(void *)' with an expression of type '<overloaded function type>'}} expected-note at -7{{candidate address cannot be taken because parameter 1 has pass_object_size attribute}} expected-note at -6{{type mismatch}}
void (*p5)(char *) = IsOverloaded;
void (*p6)(char *) = &IsOverloaded;
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