GNU and Clang C++ mode fix for members skipped by a designated initializer [GH edgcpp#260]

Author: daveedvdv-nvidia

src/Changes

@@ -1,5 +1,17 @@
 Version 7.1
 
+10/9/26  [GH #260]
+GNU and Clang C++ modes: members skipped by a designated initializer
+
+In GNU C++ modes before C++20 and in all Clang C++ modes, a member that was
+not designated, but that precedes a designated member, was zero-initialized
+instead of being initialized from its default member initializer.  That is
+now fixed.  For example, with --gnu_version=170100:
+
+  struct P { int x = 1, y = 2, z = 3; };
+  P p = { .x = 10, .z = 30 };  // p.y was previously 0.  It is now 2.
+
+
 10/9/26  [GH #27]
 Clearer diagnostic when auto is deduced from an incomplete type
 

src/cp_gen_be.c

@@ -8305,6 +8305,25 @@ one step instead of class-by-class, return TRUE.
 }  /* pm_cast_is_unambiguous */
 
 
+static a_constant_ptr first_explicit_aggr_constant(a_constant_ptr con)
+/*
+con is NULL or a constant in the list of an aggregate constant.  Return the
+first constant in that list, starting with con, that is not an implicit
+initializer for a base class or member (such initializers do not appear in
+the generated source), or NULL if there is none.
+*/
+{
+  while (con != NULL &&
+         (con->constant_for_base_class_from_constexpr_folding ||
+          con->implicit_aggr_element ||
+          (constant_is(con, ck_dynamic_init) &&
+           is_default_dynamic_init(con->variant.dynamic_init.ptr)))) {
+    con = con->next;
+  }  /* while */
+  return con;
+}  /* first_explicit_aggr_constant */
+
+
 static void gen_designator(a_constant_ptr con,
                            a_field_ptr    *field,
                            a_constant_ptr *p_eff_con,
@@ -8388,12 +8407,13 @@ brace/parenthesis delimiters around it should be suppressed.
     if (!eff_con->explicit_braces_on_aggregate &&
         !eff_con->explicit_parentheses_on_aggregate &&
         !eff_con->explicit_cast_applied) {
+      a_constant_ptr  first_con = eff_con->variant.aggregate.first_constant;
+      first_con = first_explicit_aggr_constant(first_con);
       *suppress_delims = TRUE;
-      if (eff_con->variant.aggregate.first_constant != NULL &&
-          constant_is(eff_con->variant.aggregate.first_constant,
-                      ck_designator)) {
+      if (first_con != NULL && constant_is(first_con, ck_designator)) {
         /* Do not close the designator if another one will follow
-           immediately. */
+           immediately (i.e., a chained designator, possibly preceded by
+           implicit initializers for the members it skips). */
         close = FALSE;
       }  /* if */
     }  /* if */
@@ -8603,13 +8623,7 @@ which constant is the value.
     /* Loop through the list of initializer constants. */
     /* First, skip over any implicit initializers for base classes and
        initial members; they shouldn't appear in the generated source. */
-    for (sub_con = first_con;
-         sub_con != NULL &&
-                (sub_con->constant_for_base_class_from_constexpr_folding ||
-                 sub_con->implicit_aggr_element ||
-                 (sub_con->kind == (a_constant_repr_kind)ck_dynamic_init &&
-                  is_default_dynamic_init(sub_con->variant.dynamic_init.ptr)));
-         sub_con = sub_con->next) {}
+    sub_con = first_explicit_aggr_constant(first_con);
     if (sub_con != NULL &&
         sub_con->kind == (a_constant_repr_kind)ck_init_repeat) {
       /* A ck_init_repeat constant is used to do default initialization

src/decl_inits.c

@@ -3319,6 +3319,33 @@ Return TRUE if field second follows field first in the declaration order.
 }  /* fields_are_ordered */
 
 
+static a_boolean field_range_is_designated(a_constant_ptr  aggr_con,
+                                           a_field_ptr     first,
+                                           a_field_ptr     end)
+/*
+Return TRUE if a ck_designator constant in the aggregate constant aggr_con
+designates field first or a field declared between first and end (excluding
+end itself).  That is possible only when out-of-order designators are accepted:
+E.g., in "{ .c = 3, .a = 1, .d = 4 }", c lies between b (the field following
+a) and d.
+*/
+{
+  a_boolean       result = FALSE;
+  a_constant_ptr  con;
+
+  for (con = aggr_con->variant.aggregate.first_constant;
+       con != NULL && !result;
+       con = con->next) {
+    if (constant_is(con, ck_designator) &&
+        con->variant.designator.is_field_designator) {
+      a_field_ptr  fp = con->variant.designator.variant.field;
+      result = fields_are_ordered(first, fp) && !fields_are_ordered(end, fp);
+    }  /* if */
+  }  /* for */
+  return result;
+}  /* field_range_is_designated */
+
+
 static void aggr_init_field_designator(an_init_component_ptr  *p_icp,
                                        a_type_ptr             class_type,
                                        an_init_state          *is,
@@ -3561,18 +3588,23 @@ initialization. */
   }  /* if */
   if (okay) {
     if ((orig_field != *field || *p_bcp != NULL ) &&
-        cpp20_designators_restriction && !is->init_error &&
-        !is->check_validity_only && orig_field != NULL &&
-        !type_is(class_type, tk_union)) {
-    /* C++20 designators can cause base classes and certain members to
-       be skipped. Initialize those members before initializing the
-       designated member. If we found an error, we shouldn't proceed with
-       the initialization of remaining members, as the designators
-       may not be in order.  If orig_field is NULL, we have already
-       initialized all the members and this designator is invalid. It is
-       possible that it has not been diagnosed as invalid yet, so we
-       check orig_field here just in case.  If we're checking validity only,
-       there's no need to initialize the remainder. */
+        !is->init_error && !is->check_validity_only && orig_field != NULL &&
+        !type_is(class_type, tk_union) &&
+        (cpp20_designators_restriction || gpp_version_is(>= 80000) ||
+         (clang_mode && !C_mode() && fields_are_ordered(orig_field, *field) &&
+          !field_range_is_designated(aggr_con, orig_field, *field)))) {
+    /* C++ designators can cause base classes and certain members to
+       be skipped. Initialize those members (e.g., using their default member
+       initializers) before initializing the designated member. If we found
+       an error, we shouldn't proceed with the initialization of remaining
+       members, as the designators may not be in order.  If orig_field is
+       NULL, we have already initialized all the members and this designator
+       is invalid. It is possible that it has not been diagnosed as invalid
+       yet, so we check orig_field here just in case.  If we're checking
+       validity only, there's no need to initialize the remainder.  Clang
+       accepts out-of-order designators (with a warning), so in that mode the
+       skipped members are initialized only if the designator does not go
+       backward and none of them was designated earlier. */
        aggr_init_class_remainder_if_needed(aggr_con, class_type, orig_field,
                                            *p_bcp, is, diag_pos, *field);
        *p_bcp = NULL;

tests/expectations/edg_x86_64/imported.log

@@ -1424,9 +1424,6 @@ clang/cpp/SemaCXX/unavailable_aligned_allocation.sft.cpp:fn:-DTEST_NUMBER=7 --c+
 clang/cpp/SemaCXX/unavailable_aligned_allocation.sft.cpp:fn:-DTEST_NUMBER=8 --c++17 -DWATCHOS -w --exceptions:FAIL:
 clang/cpp/SemaCXX/unavailable_aligned_allocation.sft.cpp:fn:-DTEST_NUMBER=9 --c++17 -DNO_ERRORS --exceptions:FAIL:
 clang/cpp/SemaCXX/undefined-inline.sft.cpp:fp:-DTEST_NUMBER=1 -w --c++11:FAIL:
-clang/cpp/SemaCXX/uninitialized.sft.cpp:fp:-DTEST_NUMBER=1 --c++17:ABORT:
-clang/cpp/SemaCXX/uninitialized.sft.cpp:fp:-DTEST_NUMBER=2 --c++17:ABORT:
-clang/cpp/SemaCXX/uninitialized.sft.cpp:fp:-DTEST_NUMBER=3 --c++20:ABORT:
 clang/cpp/SemaCXX/unqualified-std-call-fixits.sft.cpp:fp:-DTEST_NUMBER=1 --c++20:FAIL:
 clang/cpp/SemaCXX/unqualified-std-call-fixits.sft.cpp:fp:-DTEST_NUMBER=2 --c++20:FAIL:
 clang/cpp/SemaCXX/unqualified-std-call-fixits.sft.cpp:fp:-DTEST_NUMBER=3 --c++20:FAIL:
@@ -7195,7 +7192,6 @@ gnu/cpp/diagnostic/alignof3.sft.cpp:fn:-DTEST_NUMBER=1:FAIL:
 gnu/cpp/diagnostic/auto1.sft.cpp:fp:-DTEST_NUMBER=1 --c++17:FAIL:
 gnu/cpp/diagnostic/bad-binary-ops-highlight-colors.sft.cpp:fp:-DTEST_NUMBER=1:FAIL:
 gnu/cpp/diagnostic/bad-binary-ops-no-highlight-colors.sft.cpp:fp:-DTEST_NUMBER=1:FAIL:
-gnu/cpp/diagnostic/base.sft.cpp:fp:-DTEST_NUMBER=1 --c++17:ABORT:
 gnu/cpp/diagnostic/bindings1.sft.cpp:rp:-DTEST_NUMBER=1:FAIL:
 gnu/cpp/diagnostic/constexpr3.sft.cpp:fn:-DTEST_NUMBER=1 --c++14:ABORT:
 gnu/cpp/diagnostic/constexpr4.sft.cpp:fn:-DTEST_NUMBER=1 --c++11:FAIL:

tests/tests/imported/clang/cpp/CXX/dcl/dcl.init/.aggr.rto/default.1.1.txt

@@ -3,20 +3,6 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   static constexpr C c2 = { .a = 1.0, .x = 3 };
                                  ^
 
-"Test_name.c", line 86: error: static assertion failed
-  static_assert(a.a.d == string{}.d);
-  ^
-"Test_name.c", line 86: note: the final comparison was 0 == 43
-  static_assert(a.a.d == string{}.d);
-                      ^
-
-"Test_name.c", line 87: error: static assertion failed
-  static_assert(a.b == 42);
-  ^
-"Test_name.c", line 87: note: the final comparison was 0 == 42
-  static_assert(a.b == 42);
-                    ^
-
 "Test_name.c", line 112: error: an initializer cannot be specified for a flexible array member
     int y[] = { 0 };
             ^
@@ -53,4 +39,4 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   constexpr S2 y[2] = {
                ^
 
-9 errors detected in the compilation of "Test_name.c".
+7 errors detected in the compilation of "Test_name.c".

tests/tests/imported/clang/cpp/SemaCXX/.designated-initializers.rto/default.1.1.txt

@@ -1,4 +1,17 @@
 fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_version 999999 --c++11 Test_name.c
+"Test_name.c", line 48: error: no instance of constructor "Reorder::X::X" matches the argument list
+    foo n = {.y = 4, .x = 5};
+                           ^
+"Test_name.c", line 37: note: number of parameters of function "Reorder::X::X(const Reorder::X &)" does not match the call
+    struct X {
+           ^
+"Test_name.c", line 37: note: number of parameters of function "Reorder::X::X(Reorder::X &&)" does not match the call
+    struct X {
+           ^
+"Test_name.c", line 38: note: number of parameters of function "Reorder::X::X(int)" does not match the call
+      X(int n);
+      ^
+
 "Test_name.c", line 48: warning: out-of-order initializers are nonstandard in C++
     foo n = {.y = 4, .x = 5};
                       ^
@@ -35,6 +48,10 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     S s1 = {
       ^
 
+"Test_name.c", line 90: error: variable "Reorder3::s2" has an uninitialized const or reference member
+    S s2 = {
+      ^
+
 "Test_name.c", line 94: warning: out-of-order initializers are nonstandard in C++
       .b = s3.a, .a = 1,
                   ^
@@ -43,6 +60,20 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     S s3 = {
       ^
 
+"Test_name.c", line 101: error: a class or namespace qualified name is required
+    template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
+                                                              ^
+          detected during:
+            instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [1]]" at line 105
+            instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=1]" at line 119
+
+"Test_name.c", line 101: error: expected a ";"
+    template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
+                                                               ^
+          detected during:
+            instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [1]]" at line 105
+            instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=1]" at line 119
+
 "Test_name.c", line 117: warning: out-of-order initializers are nonstandard in C++
       .a = 1,
        ^
@@ -65,10 +96,6 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
             instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [2]]" at line 105
             instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=2]" at line 124
 
-"Test_name.c", line 127: warning: out-of-order initializers are nonstandard in C++
-      .a = 1
-       ^
-
 "Test_name.c", line 101: error: a class or namespace qualified name is required
     template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
                                                               ^
@@ -83,14 +110,60 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
             instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [3]]" at line 105
             instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=3]" at line 128
 
+"Test_name.c", line 127: warning: out-of-order initializers are nonstandard in C++
+      .a = 1
+       ^
+
+"Test_name.c", line 101: error: a class or namespace qualified name is required
+    template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
+                                                              ^
+          detected during:
+            instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [4]]" at line 105
+            instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=4]" at line 132
+
+"Test_name.c", line 101: error: expected a ";"
+    template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
+                                                               ^
+          detected during:
+            instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [4]]" at line 105
+            instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=4]" at line 132
+
 "Test_name.c", line 135: warning: out-of-order initializers are nonstandard in C++
       .a = 1,
        ^
 
+"Test_name.c", line 101: error: a class or namespace qualified name is required
+    template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
+                                                              ^
+          detected during:
+            instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [6]]" at line 105
+            instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=6]" at line 142
+
+"Test_name.c", line 101: error: expected a ";"
+    template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
+                                                               ^
+          detected during:
+            instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [6]]" at line 105
+            instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=6]" at line 142
+
 "Test_name.c", line 141: warning: out-of-order initializers are nonstandard in C++
       .e = {4, 4}
        ^
 
+"Test_name.c", line 101: error: a class or namespace qualified name is required
+    template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
+                                                              ^
+          detected during:
+            instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [7]]" at line 105
+            instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=7]" at line 148
+
+"Test_name.c", line 101: error: expected a ";"
+    template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
+                                                               ^
+          detected during:
+            instantiation of class "NoCheckingFilledHoles::Error<T> [with T=int [7]]" at line 105
+            instantiation of "NoCheckingFilledHoles::DefaultInitIsError<N>::DefaultInitIsError(NoCheckingFilledHoles::Error<int [N]>) [with N=7]" at line 148
+
 "Test_name.c", line 101: error: a class or namespace qualified name is required
     template<typename T> struct Error { using type = typename T::type; }; // expected-error 3{{'::'}}
                                                               ^
@@ -119,4 +192,4 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                                        ^
           detected during instantiation of "void Bar<T>::Test() [with T=bool]" at line 33
 
-11 errors detected in the compilation of "Test_name.c".
+21 errors detected in the compilation of "Test_name.c".