re PR c++/83205 (ICE on structured binding with ill-formed negative std::tuple_size<T>::value)

	PR c++/83205
	* decl.c (cp_finish_decomp): Handle the case when tsize is not
	error_mark_node, but doesn't fit into uhwi.  Split up count != eltscnt
	and !tree_fits_uhwi_p (tsize) error_at calls into error_n and inform_n
	to handle plural forms properly.

	* g++.dg/cpp1z/decomp3.C: Adjust for structured binding count
	mismatch diagnostics split into error and warning with plural
	forms.
	* g++.dg/cpp1z/decomp10.C: Likewise.
	* g++.dg/cpp1z/decomp32.C: New test.

From-SVN: r255706

6 files changed, 84 insertions, 15 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index d96b679..5c28100 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,11 @@
 2017-12-15  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/83205
+	* decl.c (cp_finish_decomp): Handle the case when tsize is not
+	error_mark_node, but doesn't fit into uhwi.  Split up count != eltscnt
+	and !tree_fits_uhwi_p (tsize) error_at calls into error_n and inform_n
+	to handle plural forms properly.
+
 	PR c++/81197
 	* cp-tree.h (cp_maybe_mangle_decomp): Declare.
 	* decl.c (cp_maybe_mangle_decomp): New function.
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 0e6ee05..ca9e0c7 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -7446,11 +7446,20 @@ cp_finish_decomp (tree decl, tree first, unsigned int count)
 	{
        cnt_mismatch:
 	  if (count > eltscnt)
-	    error_at (loc, "%u names provided while %qT decomposes into "
-			   "%wu elements", count, type, eltscnt);
+	    error_n (loc, count,
+		     "%u name provided for structured binding",
+		     "%u names provided for structured binding", count);
 	  else
-	    error_at (loc, "only %u names provided while %qT decomposes into "
-			   "%wu elements", count, type, eltscnt);
+	    error_n (loc, count,
+		     "only %u name provided for structured binding",
+		     "only %u names provided for structured binding", count);
+	  /* Some languages have special plural rules even for large values,
+	     but it is periodic with period of 10, 100, 1000 etc.  */
+	  inform_n (loc, eltscnt > INT_MAX
+			 ? (eltscnt % 1000000) + 1000000 : eltscnt,
+		    "while %qT decomposes into %wu element",
+		    "while %qT decomposes into %wu elements",
+		    type, eltscnt);
 	  goto error_out;
 	}
       eltype = TREE_TYPE (type);
@@ -7519,6 +7528,15 @@ cp_finish_decomp (tree decl, tree first, unsigned int count)
 			 "constant expression", type);
 	  goto error_out;
 	}
+      if (!tree_fits_uhwi_p (tsize))
+	{
+	  error_n (loc, count,
+		   "%u name provided for structured binding",
+		   "%u names provided for structured binding", count);
+	  inform (loc, "while %qT decomposes into %E elements",
+		  type, tsize);
+	  goto error_out;
+	}
       eltscnt = tree_to_uhwi (tsize);
       if (count != eltscnt)
 	goto cnt_mismatch;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ba86d2f..7bbf0e9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,12 @@
 2017-12-15  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/83205
+	* g++.dg/cpp1z/decomp3.C: Adjust for structured binding count
+	mismatch diagnostics split into error and warning with plural
+	forms.
+	* g++.dg/cpp1z/decomp10.C: Likewise.
+	* g++.dg/cpp1z/decomp32.C: New test.
+
 	PR c++/81197
 	* g++.dg/cpp1z/decomp34.C: New test.
 
diff --git a/gcc/testsuite/g++.dg/cpp1z/decomp10.C b/gcc/testsuite/g++.dg/cpp1z/decomp10.C
index a841d35..6ed9272 100644
--- a/gcc/testsuite/g++.dg/cpp1z/decomp10.C
+++ b/gcc/testsuite/g++.dg/cpp1z/decomp10.C
@@ -11,7 +11,8 @@ void f1() { auto [ x ] = a1; }	// { dg-error "is not an integral constant expres
 
 struct A2 { int i,j; } a2;
 template<> struct std::tuple_size<A2> { enum { value = 5 }; };
-void f2() { auto [ x ] = a2; }	// { dg-error "decomposes into 5" }
+void f2() { auto [ x ] = a2; }	// { dg-error "only 1 name provided" }
+			        // { dg-message "decomposes into 5" "" { target *-*-* } .-1 }
 
 struct A3 { int i,j; } a3;
 template<> struct std::tuple_size<A3> { enum { value = 1 }; };
diff --git a/gcc/testsuite/g++.dg/cpp1z/decomp3.C b/gcc/testsuite/g++.dg/cpp1z/decomp3.C
index 71dc938..529f373 100644
--- a/gcc/testsuite/g++.dg/cpp1z/decomp3.C
+++ b/gcc/testsuite/g++.dg/cpp1z/decomp3.C
@@ -51,16 +51,21 @@ int arr[4];
 void
 test3 (A &b, B c)
 {
-  auto [ d, e, f ] = arr;		// { dg-error "only 3 names provided while 'int .4.' decomposes into 4 elements" }
-					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-1 }
-  auto & [ g, h, i, j, k ] = arr;	// { dg-error "5 names provided while 'int .4.' decomposes into 4 elements" }
-					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-1 }
-  auto [ l, m ] = b;			// { dg-error "only 2 names provided while 'A' decomposes into 3 elements" }
-					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-1 }
-  auto & [ n, o, p, q ] = b;		// { dg-error "4 names provided while 'A' decomposes into 3 elements" }
-					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-1 }
+  auto [ d, e, f ] = arr;		// { dg-error "only 3 names provided" }
+					// { dg-message "while 'int .4.' decomposes into 4 elements" "" { target *-*-* } .-1 }
+					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-2 }
+  auto & [ g, h, i, j, k ] = arr;	// { dg-error "5 names provided" }
+					// { dg-message "while 'int .4.' decomposes into 4 elements" "" { target *-*-* } .-1 }
+					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-2 }
+  auto [ l, m ] = b;			// { dg-error "only 2 names provided" }
+					// { dg-message "while 'A' decomposes into 3 elements" "" { target *-*-* } .-1 }
+					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-2 }
+  auto & [ n, o, p, q ] = b;		// { dg-error "4 names provided" }
+					// { dg-message "while 'A' decomposes into 3 elements" "" { target *-*-* } .-1 }
+					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-2 }
   auto [] { c };			// { dg-error "empty structured binding declaration" }
 					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-1 }
-  auto [ r, s ] = c;			// { dg-error "2 names provided while 'B' decomposes into 1 elements" }
-					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-1 }
+  auto [ r, s ] = c;			// { dg-error "2 names provided" }
+					// { dg-message "while 'B' decomposes into 1 element" "" { target *-*-* } .-1 }
+					// { dg-warning "structured bindings only available with -std=c..17 or -std=gnu..17" "" { target c++14_down } .-2 }
 }
diff --git a/gcc/testsuite/g++.dg/cpp1z/decomp32.C b/gcc/testsuite/g++.dg/cpp1z/decomp32.C
new file mode 100644
index 0000000..a76d0c7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/decomp32.C
@@ -0,0 +1,32 @@
+// PR c++/83205
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+struct A { int i; };
+struct B { int i; };
+namespace std {
+  template <typename T> struct tuple_size;
+  template <> struct tuple_size<A> {
+    static constexpr int value = -1;
+  };
+#ifdef __SIZEOF_INT128__
+  template <> struct tuple_size<B> {
+    static constexpr unsigned __int128 value = -1;
+  };
+#endif
+}
+
+auto [a] = A{};	// { dg-error "1 name provided" }
+		// { dg-message "while 'A' decomposes into -1 elements" "" { target *-*-* } .-1 }
+		// { dg-warning "structured bindings only available with" "" { target c++14_down } .-2 }
+#ifdef __SIZEOF_INT128__
+auto [b] = B{};	// { dg-error "1 name provided" "" { target int128 } }
+		// { dg-message "while 'B' decomposes into \[0-9xa-fXA-F]* elements" "" { target int128 } .-1 }
+		// { dg-warning "structured bindings only available with" "" { target { c++14_down && int128 } } .-2 }
+auto [c, d] = B{};	// { dg-error "2 names provided" "" { target int128 } }
+			// { dg-message "while 'B' decomposes into \[0-9xa-fXA-F]* elements" "" { target int128 } .-1 }
+			// { dg-warning "structured bindings only available with" "" { target { c++14_down && int128 } } .-2 }
+#endif
+auto [e, f, g] = A{};	// { dg-error "3 names provided" }
+			// { dg-message "while 'A' decomposes into -1 elements" "" { target *-*-* } .-1 }
+			// { dg-warning "structured bindings only available with" "" { target c++14_down } .-2 }