[clang][bytecode] Diagnose reference to non-constexpr variable of const type in C23 constexpr

clang/lib/AST/ByteCode/Interp.cpp

@@ -348,6 +348,13 @@ bool CheckConstant(InterpState &S, CodePtr OpPC, const Descriptor *Desc) {
   if (D->isConstexpr())
     return true;
 
+  // If we're evaluating the initializer for a constexpr variable in C23, we may
+  // only read other contexpr variables. Abort here since this one isn't
+  // constexpr.
+  if (const auto *VD = dyn_cast_if_present<VarDecl>(S.EvaluatingDecl);
+      VD && VD->isConstexpr() && S.getLangOpts().C23)
+    return Invalid(S, OpPC);
+
   QualType T = D->getType();
   bool IsConstant = T.isConstant(S.getASTContext());
   if (T->isIntegralOrEnumerationType()) {

clang/test/AST/ByteCode/constexpr.c

@@ -0,0 +1,370 @@
+// RUN: %clang_cc1 -std=c23 -verify=ref,both -triple x86_64 -pedantic -Wno-conversion -Wno-constant-conversion -Wno-div-by-zero %s
+// RUN: %clang_cc1 -std=c23 -verify=expected,both -triple x86_64 -pedantic -Wno-conversion -Wno-constant-conversion -Wno-div-by-zero -fexperimental-new-constant-interpreter %s
+
+// Check that constexpr only applies to variables.
+constexpr void f0() {} // both-error {{'constexpr' can only be used in variable declarations}}
+constexpr const int f1() { return 0; } // both-error {{'constexpr' can only be used in variable declarations}}
+
+constexpr struct S1 { int f; }; //both-error {{struct cannot be marked constexpr}}
+constexpr struct S2 ; // both-error {{struct cannot be marked constexpr}}
+constexpr union U1; // both-error {{union cannot be marked constexpr}}
+constexpr union U2 {int a; float b;}; // both-error {{union cannot be marked constexpr}}
+constexpr enum E1 {A = 1, B = 2} ; // both-error {{enum cannot be marked constexpr}}
+struct S3 {
+  static constexpr int f = 0; // both-error {{type name does not allow storage class}}
+  // both-error@-1 {{type name does not allow constexpr}}
+  // both-error@-2 {{expected ';' at end}}
+  constexpr int f1 = 0;
+  // both-error@-1 {{type name does not allow constexpr}}
+  // both-error@-2 {{expected ';' at end}}
+};
+
+constexpr; // both-error {{'constexpr' can only be used in variable declarations}}
+constexpr int V1 = 3;
+constexpr float V2 = 7.0;
+int V3 = (constexpr)3; // both-error {{expected expression}}
+
+void f2() {
+  constexpr int a = 0;
+  constexpr float b = 1.7f;
+}
+
+// Check how constexpr works with other storage-class specifiers.
+constexpr auto V4 = 1;
+constexpr static auto V5 = 1;
+constexpr static const auto V6 = 1;
+constexpr static const int V7 = 1;
+constexpr static int V8 = 1;
+constexpr auto Ulong = 1L;
+constexpr auto CompoundLiteral = (int){13};
+constexpr auto DoubleCast = (double)(1 / 3);
+constexpr auto String = "this is a string"; // both-error {{constexpr pointer initializer is not null}}
+constexpr signed auto Long = 1L; // both-error {{'auto' cannot be signed or unsigned}}
+_Static_assert(_Generic(Ulong, long : 1));
+_Static_assert(_Generic(CompoundLiteral, int : 1));
+_Static_assert(_Generic(DoubleCast, double : 1));
+_Static_assert(_Generic(String, char* : 1));
+
+typedef constexpr int Foo; // both-error {{typedef cannot be constexpr}}
+constexpr typedef int Bar; // both-error {{typedef cannot be constexpr}}
+
+void f3(constexpr register int P1) { // both-error {{function parameter cannot be constexpr}}
+  constexpr register int V9 = 0;
+  constexpr register auto V10 = 0.0;
+}
+
+constexpr thread_local int V11 = 38; // both-error {{cannot combine with previous '_Thread_local' declaration specifier}}
+constexpr static thread_local double V12 = 38; // both-error {{cannot combine with previous '_Thread_local' declaration specifier}}
+constexpr extern thread_local char V13; // both-error {{cannot combine with previous '_Thread_local' declaration specifier}}
+// both-error@-1 {{cannot combine with previous 'extern' declaration specifier}}
+// both-error@-2 {{constexpr variable declaration must be a definition}}
+constexpr thread_local short V14 = 38; // both-error {{cannot combine with previous '_Thread_local' declaration specifier}}
+
+// Check how constexpr works with qualifiers.
+constexpr _Atomic int V15 = 0; // both-error {{constexpr variable cannot have type 'const _Atomic(int)'}}
+constexpr _Atomic(int) V16 = 0; // both-error {{constexpr variable cannot have type 'const _Atomic(int)'}}
+
+constexpr volatile int V17 = 0; // both-error {{constexpr variable cannot have type 'const volatile int'}}
+
+constexpr int * restrict V18 = 0; // both-error {{constexpr variable cannot have type 'int *const restrict'}}
+
+constexpr extern char Oops = 1; // both-error {{cannot combine with previous 'extern' declaration specifier}} \
+                                // both-warning {{'extern' variable has an initializer}}
+
+constexpr int * restrict * Oops1 = 0;
+
+typedef _Atomic(int) TheA;
+typedef volatile short TheV;
+typedef float * restrict TheR;
+
+constexpr TheA V19[3] = {};
+// both-error@-1 {{constexpr variable cannot have type 'const TheA[3]' (aka 'const _Atomic(int)[3]')}}
+constexpr TheV V20[3] = {};
+// both-error@-1 {{constexpr variable cannot have type 'const TheV[3]' (aka 'const volatile short[3]')}}
+constexpr TheR V21[3] = {};
+// both-error@-1 {{constexpr variable cannot have type 'const TheR[3]' (aka 'float *restrict const[3]')}}
+
+struct HasA {
+  TheA f;
+  int b;
+};
+
+struct HasV {
+  float b;
+  TheV f;
+};
+
+struct HasR {
+  short b;
+  int a;
+  TheR f;
+};
+
+constexpr struct HasA V22[2] = {};
+// both-error@-1 {{constexpr variable cannot have type 'TheA' (aka '_Atomic(int)')}}
+constexpr struct HasV V23[2] = {};
+// both-error@-1 {{constexpr variable cannot have type 'TheV' (aka 'volatile short')}}
+constexpr struct HasR V24[2] = {};
+// both-error@-1 {{constexpr variable cannot have type 'TheR' (aka 'float *restrict')}}
+
+union U3 {
+  float a;
+  union {
+    struct HasA f;
+    struct HasR f1;
+  };
+};
+
+constexpr union U3 V25 = {};
+// both-error@-1 {{constexpr variable cannot have type 'TheA' (aka '_Atomic(int)')}}
+constexpr union U3 V26[8] = {};
+// both-error@-1 {{constexpr variable cannot have type 'TheA' (aka '_Atomic(int)')}}
+
+struct S4 {
+  union U3 f[3];
+};
+
+constexpr struct S4 V27 = {};
+// both-error@-1 {{constexpr variable cannot have type 'TheA' (aka '_Atomic(int)')}}
+constexpr const int V28 = 28;
+
+struct S {
+  union {
+    volatile int i;
+  };
+  int j;
+};
+
+constexpr struct S s = {}; // both-error {{constexpr variable cannot have type 'volatile int'}}
+
+// Check that constexpr variable must have a valid initializer which is a
+// constant expression.
+constexpr int V29;
+// both-error@-1 {{constexpr variable 'V29' must be initialized by a constant expression}}
+
+struct S5 {
+  int f;
+};
+
+constexpr struct S5 V30;
+// both-error@-1 {{constexpr variable 'V30' must be initialized by a constant expression}}
+constexpr struct S5 V31 = {};
+
+int randomFoo() { return 7; }
+
+constexpr float V32 = randomFoo();
+// both-error@-1 {{constexpr variable 'V32' must be initialized by a constant expression}}
+
+const int V33 = 4;
+const int V34 = 0;
+const int V35 = 2;
+
+constexpr int V36 = V33 / V34;
+// both-error@-1 {{constexpr variable 'V36' must be initialized by a constant expression}}
+constexpr int V37 = V33 / V35;
+// both-error@-1 {{constexpr variable 'V37' must be initialized by a constant expression}}
+constexpr int V38 = 3;
+constexpr int V39 = V38 / V38;
+constexpr int V40 = V38 / 2;
+constexpr int V41 = V38 / 0;
+// both-error@-1 {{constexpr variable 'V41' must be initialized by a constant expression}}
+// both-note@-2 {{division by zero}}
+constexpr int V42 = V38 & 0;
+
+constexpr struct S5 V43 = { randomFoo() };
+// both-error@-1 {{constexpr variable 'V43' must be initialized by a constant expression}}
+constexpr struct S5 V44 = { 0 };
+constexpr struct S5 V45 = { V38 / 0 };
+// both-error@-1 {{constexpr variable 'V45' must be initialized by a constant expression}}
+// both-note@-2 {{division by zero}}
+
+constexpr float V46[3] = {randomFoo() };
+// both-error@-1 {{constexpr variable 'V46' must be initialized by a constant expression}}
+constexpr struct S5 V47[3] = {randomFoo() };
+// both-error@-1 {{constexpr variable 'V47' must be initialized by a constant expression}}
+
+const static int V48 = V38;
+constexpr static int V49 = V48;
+// both-error@-1 {{constexpr variable 'V49' must be initialized by a constant expression}}
+
+void f4(const int P1) {
+  constexpr int V = P1;
+// both-error@-1 {{constexpr variable 'V' must be initialized by a constant expression}}
+
+  constexpr int V1 = 12;
+  constexpr const int *V2 = &V1;
+// both-error@-1 {{constexpr variable 'V2' must be initialized by a constant expression}}
+}
+
+// Check that initializer for constexpr variable should match the type of the
+// variable and is exactly representable int the variable's type.
+
+struct S6 {
+  unsigned char a;
+};
+
+struct S7 {
+  union {
+    float a;
+  };
+  unsigned int b;
+};
+
+struct S8 {
+  unsigned char a[3];
+  unsigned int b[3];
+};
+
+constexpr struct S8 DesigInit = {.b = {299, 7, 8}, .a = {-1, 7, 8}};
+// both-error@-1 {{constexpr initializer evaluates to -1 which is not exactly representable in type 'unsigned char'}}
+
+void f5() {
+  constexpr char V50 = 300;
+  // both-error@-1 {{constexpr initializer evaluates to 300 which is not exactly representable in type 'const char'}}
+  constexpr float V51 = 1.0 / 3.0;
+  // both-error@-1 {{constexpr initializer evaluates to 3.333333e-01 which is not exactly representable in type 'const float'}}
+  constexpr float V52 = 0.7;
+  // both-error@-1 {{constexpr initializer evaluates to 7.000000e-01 which is not exactly representable in type 'const float'}}
+  constexpr float V53 = 1.0f / 3.0f;
+  constexpr float V54 = 432000000000;
+  // both-error@-1 {{constexpr initializer evaluates to 432000000000 which is not exactly representable in type 'const float'}}
+  constexpr unsigned char V55[] = {
+      "\xAF",
+  // both-error@-1 {{constexpr initializer evaluates to -81 which is not exactly representable in type 'const unsigned char'}}
+  };
+
+  constexpr unsigned char V56[] = {
+      u8"\xAF",
+  };
+  constexpr struct S6 V57 = {299};
+  // both-error@-1 {{constexpr initializer evaluates to 299 which is not exactly representable in type 'unsigned char'}}
+  constexpr struct S6 V58 = {-299};
+  // both-error@-1 {{constexpr initializer evaluates to -299 which is not exactly representable in type 'unsigned char'}}
+  constexpr double V59 = 0.5;
+  constexpr double V60 = 1.0;
+  constexpr float V61 = V59 / V60;
+  constexpr double V62 = 1.7;
+  constexpr float V63 = V59 / V62;
+  // both-error@-1 {{constexpr initializer evaluates to 2.941176e-01 which is not exactly representable in type 'const float'}}
+
+  constexpr unsigned char V64 = '\xAF';
+  // both-error@-1 {{constexpr initializer evaluates to -81 which is not exactly representable in type 'const unsigned char'}}
+  constexpr unsigned char V65 = u8'\xAF';
+
+  constexpr char V66[3] = {300};
+  // both-error@-1 {{constexpr initializer evaluates to 300 which is not exactly representable in type 'const char'}}
+  constexpr struct S6 V67[3] = {300};
+  // both-error@-1 {{constexpr initializer evaluates to 300 which is not exactly representable in type 'unsigned char'}}
+
+  constexpr struct S7 V68 = {0.3, -1 };
+  // both-error@-1 {{constexpr initializer evaluates to 3.000000e-01 which is not exactly representable in type 'float'}}
+  // both-error@-2 {{constexpr initializer evaluates to -1 which is not exactly representable in type 'unsigned int'}}
+  constexpr struct S7 V69 = {0.5, -1 };
+  // both-error@-1 {{constexpr initializer evaluates to -1 which is not exactly representable in type 'unsigned int'}}
+  constexpr struct S7 V70[3] = {{123456789}};
+  // both-error@-1 {{constexpr initializer evaluates to 123456789 which is not exactly representable in type 'float'}}
+
+  constexpr int V71 = 0.3;
+  // both-error@-1 {{constexpr initializer for type 'const int' is of type 'double'}}
+  constexpr int V72 = V59;
+  // both-error@-1 {{constexpr initializer for type 'const int' is of type 'const double'}}
+  constexpr struct S6 V73 = {V59};
+  // both-error@-1 {{constexpr initializer for type 'unsigned char' is of type 'const double'}}
+
+  constexpr float V74 = 1;
+  constexpr float V75 = V59;
+  constexpr unsigned int V76[3] = {0.5};
+  // both-error@-1 {{constexpr initializer for type 'const unsigned int' is of type 'double'}}
+
+  constexpr _Complex float V77 = 0;
+  constexpr float V78 = V77;
+  // both-error@-1 {{constexpr initializer for type 'const float' is of type 'const _Complex float'}}
+  constexpr int V79 = V77;
+  // both-error@-1 {{constexpr initializer for type 'const int' is of type 'const _Complex float'}}
+
+}
+
+constexpr char string[] = "test""ing this out\xFF";
+constexpr unsigned char ustring[] = "test""ing this out\xFF";
+// both-error@-1 {{constexpr initializer evaluates to -1 which is not exactly representable in type 'const unsigned char'}}
+constexpr char u8string[] = u8"test"u8"ing this out\xFF";
+// both-error@-1 {{constexpr initializer evaluates to 255 which is not exactly representable in type 'const char'}}
+constexpr unsigned char u8ustring[] = u8"test"u8"ing this out\xFF";
+constexpr unsigned short uustring[] = u"test"u"ing this out\xFF";
+constexpr unsigned int Ustring[] = U"test"U"ing this out\xFF";
+constexpr unsigned char Arr2[6][6] = {
+  {"ek\xFF"}, {"ek\xFF"}
+// both-error@-1 2{{constexpr initializer evaluates to -1 which is not exactly representable in type 'const unsigned char'}}
+};
+
+constexpr int i = (12);
+constexpr int j = (i);
+constexpr unsigned jneg = (-i);
+// both-error@-1 {{constexpr initializer evaluates to -12 which is not exactly representable in type 'const unsigned int'}}
+
+// Check that initializer for pointer constexpr variable should be null.
+constexpr int V80 = 3;
+constexpr const int *V81 = &V80;
+// both-error@-1 {{constexpr pointer initializer is not null}}
+constexpr int *V82 = 0;
+constexpr int *V83 = V82;
+constexpr int *V84 = 42;
+// ref-error@-1 {{constexpr variable 'V84' must be initialized by a constant expression}}
+// ref-note@-2 {{this conversion is not allowed in a constant expression}}
+// both-error@-3 {{constexpr pointer initializer is not null}}
+constexpr int *V85 = nullptr;
+
+// Check that constexpr variables should not be VLAs.
+void f6(const int P1) {
+  constexpr int V86[P1] = {};
+// both-error@-1 {{constexpr variable cannot have type 'const int[P1]'}}
+  const int V87 = 3;
+  constexpr int V88[V87] = {};
+// both-warning@-1 {{variable length array folded to constant array as an extension}}
+  int V89 = 7;
+  constexpr int V90[V89] = {};
+// both-error@-1 {{constexpr variable cannot have type 'const int[V89]'}}
+}
+
+void f7(int n, int array[n]) {
+  constexpr typeof(array) foo = 0; // Accepted because array is a pointer type, not a VLA type
+  int (*(*fp)(int n))[n];
+  constexpr typeof(fp) bar = 0; // both-error {{constexpr variable cannot have type 'const typeof (fp)' (aka 'int (*(*const)(int))[n]')}}
+}
+
+// Check how constexpr works with NaNs and infinities.
+#define FLT_NAN __builtin_nanf("1")
+#define DBL_NAN __builtin_nan("1")
+#define LD_NAN __builtin_nanf("1")
+#define FLT_SNAN __builtin_nansf("1")
+#define DBL_SNAN __builtin_nans("1")
+#define LD_SNAN __builtin_nansl("1")
+#define INF __builtin_inf()
+void infsNaNs() {
+  // Inf and quiet NaN is always fine, signaling NaN must have the same type.
+  constexpr float fl0 = INF;
+  constexpr float fl1 = (long double)INF;
+  constexpr float fl2 = (long double)FLT_NAN;
+  constexpr float fl3 = FLT_NAN;
+  constexpr float fl5 = DBL_NAN;
+  constexpr float fl6 = LD_NAN;
+  constexpr float fl7 = DBL_SNAN; // both-error {{constexpr initializer evaluates to nan which is not exactly representable in type 'const float'}}
+  constexpr float fl8 = LD_SNAN; // both-error {{constexpr initializer evaluates to nan which is not exactly representable in type 'const float'}}
+
+  constexpr double db0 = FLT_NAN;
+  constexpr double db2 = DBL_NAN;
+  constexpr double db3 = DBL_SNAN;
+  constexpr double db4 = FLT_SNAN; // both-error {{constexpr initializer evaluates to nan which is not exactly representable in type 'const double'}}
+  constexpr double db5 = LD_SNAN; // both-error {{constexpr initializer evaluates to nan which is not exactly representable in type 'const double'}}
+  constexpr double db6 = INF;
+}
+
+constexpr struct S9 s9 = {  }; // both-error {{variable has incomplete type 'const struct S9'}} \
+                               // both-note {{forward declaration of 'struct S9'}}
+
+struct S10 {
+  signed long long i : 8;
+};
+constexpr struct S10 c = { 255 };
+// FIXME-expected-error@-1 {{constexpr initializer evaluates to 255 which is not exactly representable in 'long long' bit-field with width 8}}
+// See: GH#101299