[Sema] Note when we encounter a problem in ExprConstant.
Currently, the constexpr evaluator is very conservative about unmodeled
side-effects when we're evaluating an expression in a mode that allows
such side-effects.
This patch makes us note when we might have actually encountered an
unmodeled side-effect, which allows us to be more accurate when we know
an unmodeled side-effect couldn't have occurred.
This patch has been split into two commits; this one primarily
introduces the bits necessary to track whether we might have potentially
hit such a side-effect. The one that actually does the tracking (which
boils down to more or less a rename of keepEvaluatingAfterFailure to
noteFailure) is coming soon.
Differential Revision: http://reviews.llvm.org/D18540
llvm-svn: 270781
diff --git a/clang/test/SemaCXX/builtin-object-size-cxx14.cpp b/clang/test/SemaCXX/builtin-object-size-cxx14.cpp
new file mode 100644
index 0000000..32d752d
--- /dev/null
+++ b/clang/test/SemaCXX/builtin-object-size-cxx14.cpp
@@ -0,0 +1,99 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++14 %s
+
+namespace basic {
+// Ensuring that __bos can be used in constexpr functions without anything
+// sketchy going on...
+constexpr int bos0() {
+ int k = 5;
+ char cs[10] = {};
+ return __builtin_object_size(&cs[k], 0);
+}
+
+constexpr int bos1() {
+ int k = 5;
+ char cs[10] = {};
+ return __builtin_object_size(&cs[k], 1);
+}
+
+constexpr int bos2() {
+ int k = 5;
+ char cs[10] = {};
+ return __builtin_object_size(&cs[k], 2);
+}
+
+constexpr int bos3() {
+ int k = 5;
+ char cs[10] = {};
+ return __builtin_object_size(&cs[k], 3);
+}
+
+static_assert(bos0() == sizeof(char) * 5, "");
+static_assert(bos1() == sizeof(char) * 5, "");
+static_assert(bos2() == sizeof(char) * 5, "");
+static_assert(bos3() == sizeof(char) * 5, "");
+}
+
+namespace in_enable_if {
+// The code that prompted these changes was __bos in enable_if
+
+void copy5CharsInto(char *buf) // expected-note{{candidate}}
+ __attribute__((enable_if(__builtin_object_size(buf, 0) != -1 &&
+ __builtin_object_size(buf, 0) > 5,
+ "")));
+
+// We use different EvalModes for __bos with type 0 versus 1. Ensure 1 works,
+// too...
+void copy5CharsIntoStrict(char *buf) // expected-note{{candidate}}
+ __attribute__((enable_if(__builtin_object_size(buf, 1) != -1 &&
+ __builtin_object_size(buf, 1) > 5,
+ "")));
+
+struct LargeStruct {
+ int pad;
+ char buf[6];
+ int pad2;
+};
+
+struct SmallStruct {
+ int pad;
+ char buf[5];
+ int pad2;
+};
+
+void noWriteToBuf() {
+ char buf[6];
+ copy5CharsInto(buf);
+
+ LargeStruct large;
+ copy5CharsIntoStrict(large.buf);
+}
+
+void initTheBuf() {
+ char buf[6] = {};
+ copy5CharsInto(buf);
+
+ LargeStruct large = {0, {}, 0};
+ copy5CharsIntoStrict(large.buf);
+}
+
+int getI();
+void initTheBufWithALoop() {
+ char buf[6] = {};
+ for (unsigned I = getI(); I != sizeof(buf); ++I)
+ buf[I] = I;
+ copy5CharsInto(buf);
+
+ LargeStruct large;
+ for (unsigned I = getI(); I != sizeof(buf); ++I)
+ large.buf[I] = I;
+ copy5CharsIntoStrict(large.buf);
+}
+
+void tooSmallBuf() {
+ char buf[5];
+ copy5CharsInto(buf); // expected-error{{no matching function for call}}
+
+ SmallStruct small;
+ copy5CharsIntoStrict(small.buf); // expected-error{{no matching function for call}}
+}
+}
diff --git a/clang/test/SemaCXX/constant-expression-cxx1y.cpp b/clang/test/SemaCXX/constant-expression-cxx1y.cpp
index e9ecbe8..d67cbf6 100644
--- a/clang/test/SemaCXX/constant-expression-cxx1y.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx1y.cpp
@@ -179,12 +179,10 @@
static_assert(!test1(100), "");
static_assert(!test1(101), ""); // expected-error {{constant expression}} expected-note {{in call to 'test1(101)'}}
- // FIXME: We should be able to reject this before it's called
- constexpr void f() {
+ constexpr void f() { // expected-error{{constexpr function never produces a constant expression}} expected-note@+2{{assignment to dereferenced one-past-the-end pointer is not allowed in a constant expression}}
char foo[10] = { "z" }; // expected-note {{here}}
- foo[10] = 'x'; // expected-warning {{past the end}} expected-note {{assignment to dereferenced one-past-the-end pointer}}
+ foo[10] = 'x'; // expected-warning {{past the end}}
}
- constexpr int k = (f(), 0); // expected-error {{constant expression}} expected-note {{in call}}
}
namespace array_resize {
@@ -938,3 +936,16 @@
constexpr int testb = f(e2, 3); // expected-error {{constant expression}} expected-note {{in call}}
constexpr int testc = f(e3, 3);
}
+
+namespace SpeculativeEvalWrites {
+ // Ensure that we don't try to speculatively evaluate writes.
+ constexpr int f() {
+ int i = 0;
+ int a = 0;
+ // __builtin_object_size speculatively evaluates its first argument.
+ __builtin_object_size((i = 1, &a), 0);
+ return i;
+ }
+
+ static_assert(!f(), "");
+}