[PATCH] D137488: [clang][Interp] Array initialization via string literal

[Timm Bäder via Phabricator via cfe-commits]

tbaeder updated this revision to Diff 477409.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D137488/new/

https://reviews.llvm.org/D137488

Files:
  clang/lib/AST/Interp/ByteCodeExprGen.cpp
  clang/test/AST/Interp/literals.cpp


Index: clang/test/AST/Interp/literals.cpp
===================================================================
--- clang/test/AST/Interp/literals.cpp
+++ clang/test/AST/Interp/literals.cpp
@@ -350,6 +350,46 @@
 #endif
 
 #pragma clang diagnostic pop
+
+  constexpr char foo[12] = "abc";
+  static_assert(foo[0] == 'a', "");
+  static_assert(foo[1] == 'b', "");
+  static_assert(foo[2] == 'c', "");
+  static_assert(foo[3] == 0, "");
+  static_assert(foo[11] == 0, "");
+
+  constexpr char foo2[] = "abc\0def";
+  static_assert(foo2[0] == 'a', "");
+  static_assert(foo2[3] == '\0', "");
+  static_assert(foo2[6] == 'f', "");
+  static_assert(foo2[7] == '\0', "");
+  static_assert(foo2[8] == '\0', ""); // expected-error {{not an integral constant expression}} \
+                                      // expected-note {{read of dereferenced one-past-the-end pointer}} \
+                                      // ref-error {{not an integral constant expression}} \
+                                      // ref-note {{read of dereferenced one-past-the-end pointer}}
+
+  constexpr char foo3[4] = "abc";
+  static_assert(foo3[3] == '\0', "");
+  static_assert(foo3[4] == '\0', ""); // expected-error {{not an integral constant expression}} \
+                                      // expected-note {{read of dereferenced one-past-the-end pointer}} \
+                                      // ref-error {{not an integral constant expression}} \
+                                      // ref-note {{read of dereferenced one-past-the-end pointer}}
+
+  constexpr char foo4[2] = "abcd"; // expected-error {{initializer-string for char array is too long}} \
+                                   // ref-error {{initializer-string for char array is too long}}
+  static_assert(foo4[0] == 'a', "");
+  static_assert(foo4[1] == 'b', "");
+  static_assert(foo4[2] == '\0', ""); // expected-error {{not an integral constant expression}} \
+                                      // expected-note {{read of dereferenced one-past-the-end pointer}} \
+                                      // ref-error {{not an integral constant expression}} \
+                                      // ref-note {{read of dereferenced one-past-the-end pointer}}
+
+constexpr char foo5[12] = "abc\xff";
+#if defined(__CHAR_UNSIGNED__) || __CHAR_BIT__ > 8
+static_assert(foo5[3] == 255, "");
+#else
+static_assert(foo5[3] == -1, "");
+#endif
 };
 
 #if __cplusplus > 201402L
Index: clang/lib/AST/Interp/ByteCodeExprGen.cpp
===================================================================
--- clang/lib/AST/Interp/ByteCodeExprGen.cpp
+++ clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -1073,6 +1073,33 @@
         return false;
     }
     return true;
+  } else if (const auto *SL = dyn_cast<StringLiteral>(Initializer)) {
+    const ConstantArrayType *CAT =
+        Ctx.getASTContext().getAsConstantArrayType(SL->getType());
+    assert(CAT && "a string literal that's not a constant array?");
+
+    // If the initializer string is too long, a diagnostic has already been
+    // emitted. Read only the array length from the string literal.
+    unsigned N = std::min(unsigned(CAT->getSize().getZExtValue()), SL->getLength());
+    size_t CharWidth = SL->getCharByteWidth();
+
+    for (unsigned I = 0; I != N; ++I) {
+      uint32_t CodeUnit = SL->getCodeUnit(I);
+
+      if (CharWidth == 1) {
+        this->emitConstSint8(CodeUnit, SL);
+        this->emitInitElemSint8(I, SL);
+      } else if (CharWidth == 2) {
+        this->emitConstUint16(CodeUnit, SL);
+        this->emitInitElemUint16(I, SL);
+      } else if (CharWidth == 4) {
+        this->emitConstUint32(CodeUnit, SL);
+        this->emitInitElemUint32(I, SL);
+      } else {
+        llvm_unreachable("unsupported character width");
+      }
+    }
+    return true;
   }
 
   assert(false && "Unknown expression for array initialization");


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