[C] Allow __attribute__((nonstring)) on multidimensional arrays (#138133)

This addresses post-commit review feedback from the Linux kernel folks
and improves compatibility with the same feature in GCC

clang/lib/Sema/SemaInit.cpp

@@ -261,8 +261,22 @@ static void CheckStringInit(Expr *Str, QualType &DeclT, const ArrayType *AT,
           << Str->getSourceRange();
     else if (StrLength - 1 == ArrayLen) {
       // If the entity being initialized has the nonstring attribute, then
-      // silence the "missing nonstring" diagnostic.
-      if (const ValueDecl *D = Entity.getDecl();
+      // silence the "missing nonstring" diagnostic. If there's no entity,
+      // check whether we're initializing an array of arrays; if so, walk the
+      // parents to find an entity.
+      auto FindCorrectEntity =
+          [](const InitializedEntity *Entity) -> const ValueDecl * {
+        while (Entity) {
+          if (const ValueDecl *VD = Entity->getDecl())
+            return VD;
+          if (!Entity->getType()->isArrayType())
+            return nullptr;
+          Entity = Entity->getParent();
+        }
+
+        return nullptr;
+      };
+      if (const ValueDecl *D = FindCorrectEntity(&Entity);
           !D || !D->hasAttr<NonStringAttr>())
         S.Diag(
             Str->getBeginLoc(),

clang/test/Sema/attr-nonstring.c

@@ -2,7 +2,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify=noncxx,expected,no-nonstring -Wextra %s
 // RUN: %clang_cc1 -fsyntax-only -verify=noncxx,expected,compat -Wc++-unterminated-string-initialization %s
 // RUN: %clang_cc1 -fsyntax-only -verify=noncxx,expected,compat -Wc++-compat %s
-// RUN: %clang_cc1 -fsyntax-only -verify=expected,cxx -x c++ %s
+// RUN: %clang_cc1 -fsyntax-only -verify=expected,cxx -x c++ -Wno-c99-designator %s
 // RUN: %clang_cc1 -fsyntax-only -verify=expected,noncxx -Wno-unterminated-string-initialization %s
 // RUN: %clang_cc1 -fsyntax-only -verify=expected,noncxx -Wc++-compat -Wextra -Wno-unterminated-string-initialization -Wno-c++-unterminated-string-initialization %s
 
@@ -39,3 +39,193 @@ __attribute__((nonstring)) int eek2;              // expected-warning {{'nonstri
 // diagnostic when you overwrite more than just the null terminator.
 char too_big[3] = "this is too big"; // noncxx-warning {{initializer-string for char array is too long}} \
                                         cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 16 (including the null terminating character)}}
+
+// Show that this also applies to arrays of objects containing strings, too.
+const char md_array[][3] __attribute__((nonstring)) = { "BAR", "FOO", };   // compat-warning 2 {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                                                                              cxx-error 2 {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+
+struct StructWithArrays {
+  char string[3];
+  __attribute__((nonstring)) char nonstring[3];
+};
+
+struct StructWithArrays s1[] = {
+  {
+    "FOO", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+              compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+              cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+    "BAR", // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+              cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+  },
+  {
+    "BAZ", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+              compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+              cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+    "BIP", // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+              cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+  }
+};
+
+struct Inner {
+  struct StructWithArrays s[2];
+};
+struct Outer {
+  struct Inner i[2];
+};
+
+struct Outer o1[] = { // Array of Outer
+  { // Outer
+    { // Array of Inner
+      { // Inner
+        { // Array of StructWithArrays
+          { // StructWithArrays
+            "FOO", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                      compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+            "BAR"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+          },
+          { // StructWithArrays
+            "BAZ", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                      compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+            "BAT"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+          }
+        } // End array of StructWithArrays
+      }, // End Inner
+      { // Inner
+        { // Array of StructWithArrays
+          { // StructWithArrays
+            "BIP", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                      compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+            "BOP"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+          },
+          { // StructWithArrays
+            "BAP", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                      compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+            "BUP"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+         }
+        } // End array of StructWithArrays
+      } // End Inner
+    } // End array of Inner
+  }, // End Outer
+  { // Outer
+    { // Array of Inner
+      { // Inner
+        { // Array of StructWithArrays
+          { // StructWithArrays
+            "ABC", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                      compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+            "CAB"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+          },
+          { // StructWithArrays
+            "BAC", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                      compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+            "CBA"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+          }
+        } // End array of StructWithArrays
+      }, // End Inner
+      { // Inner
+        { // Array of StructWithArrays
+          { // StructWithArrays
+            "XYZ", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                      compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+            "YZX"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+          },
+          { // StructWithArrays
+            "ZYX", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                      compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+            "ZXY"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                      cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+         }
+        } // End array of StructWithArrays
+      } // End Inner
+    } // End array of Inner
+  }, // End Outer
+};
+
+// Do the same test as above, but using designated initializers and a more
+// simple layout of the initialization.
+
+struct Outer o2[] = {
+  [0] = {
+    .i[0] = {
+      .s[0] = {
+        "FOO", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                  compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+        "BAR"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+      },
+      .s[1] = {
+        "BAZ", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                  compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+        "BAT"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+      }
+    },
+    .i[1] = {
+      .s[0] = {
+        "BIP", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                  compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+        "BOP"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+      },
+      .s[1] = {
+        "BAP", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                  compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+        "BUP"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+      }
+    }
+  },
+  [1] = {
+    .i[0] = {
+      .s[0] = {
+        "ABC", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                  compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+        "CAB"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+      },
+      .s[1] = {
+        "BAC", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                  compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+        "CBA"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+      }
+    },
+    .i[1] = {
+      .s[0] = {
+        "XYZ", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                  compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+        "YZX"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+      },
+      .s[1] = {
+        "ZYX", // no-nonstring-warning {{initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute?}} \
+                  compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+        "ZXY"  // compat-warning {{initializer-string for character array is too long for C++, array size is 3 but initializer has size 4 (including the null terminating character)}} \
+                  cxx-error {{initializer-string for char array is too long, array size is 3 but initializer has size 4 (including the null terminating character)}}
+      }
+    }
+  }
+};