c: error for function with external and internal linkage [PR111708]

Declaring a function with both external and internal linkage
in the same TU is translation-time UB.  Add an error for this
case as already done for objects.

	PR c/111708

gcc/c/ChangeLog:

	* c-decl.cc (grokdeclarator): Add error.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr111708-1.c: New test.
	* gcc.dg/pr111708-2.c: New test.

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 5822faf01b48b9b93bb86fab5dc34a261d28b2bb..0de3847830412d44f68a815700bf75a452e34125 100644 (file)
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -8032,6 +8032,27 @@ grokdeclarator (const struct c_declarator *declarator,
                TREE_THIS_VOLATILE (decl) = 1;
              }
          }
+
+       /* C99 6.2.2p7: It is invalid (compile-time undefined
+          behavior) to create an 'extern' declaration for a
+          function if there is a global declaration that is
+          'static' and the global declaration is not visible.
+          (If the static declaration _is_ currently visible,
+          the 'extern' declaration is taken to refer to that decl.) */
+       if (!initialized
+           && TREE_PUBLIC (decl)
+           && current_scope != file_scope)
+         {
+           tree global_decl  = identifier_global_value (declarator->u.id.id);
+           tree visible_decl = lookup_name (declarator->u.id.id);
+
+           if (global_decl
+               && global_decl != visible_decl
+               && VAR_OR_FUNCTION_DECL_P (global_decl)
+               && !TREE_PUBLIC (global_decl))
+             error_at (loc, "function previously declared %<static%> "
+                       "redeclared %<extern%>");
+         }
       }
     else
       {

diff --git a/gcc/testsuite/gcc.dg/pr111708-1.c b/gcc/testsuite/gcc.dg/pr111708-1.c
new file mode 100644 (file)
index 0000000..4af7f53
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr111708-1.c
@@ -0,0 +1,42 @@
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+extern int a(void);    // external linkage (6.2.2p4)
+static int a(void);    /* { dg-error "static declaration of 'a' follows non-static declaration" } */
+
+static int b(void);    // internal linkage (6.2.2p3)
+extern int b(void);    // internal linkage (6.2.2p4)
+
+static int h0(void);
+
+void s(void)
+{
+       extern int h0(void);    // internal linkage (6.2.2p4),
+       extern int h0(void);    // internal linkage (6.2.2p4), redeclaration, ok
+       extern int h2(void);    // external linkage (6.2.2p4)
+       extern int h2(void);    // external linkage (6.2.2p4), redeclaration, ok.
+}
+
+
+extern int i(void);    // external linkage (6.2.2p4)
+static int j(void);    // internal linkage (6.2.2p3)
+
+void bar(void)
+{
+       extern int i(void);     // external linkage (6.2.2p4), ok
+}
+
+void foo(void)
+{
+       extern int j(void);     // internal linkage (6.2.2p4), ok, internal
+}
+
+void x(void)
+{
+       int i(void);            // no linkage (6.2.2p6)
+       int j;                  // no linkage (6.2.2p6)
+       {
+               extern int j(void);     /* { dg-error "function previously declared 'static' redeclared 'extern'" } */
+       }
+}
+

diff --git a/gcc/testsuite/gcc.dg/pr111708-2.c b/gcc/testsuite/gcc.dg/pr111708-2.c
new file mode 100644 (file)
index 0000000..065c052
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr111708-2.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "" } */
+/* { dg-require-effective-target trampolines } */
+
+static void pp(void)
+{
+       int pp;
+       {
+               auto void pp(void);
+               void pp(void) { }
+       }
+}
+
+static void q2(void);
+
+static void qq(void)
+{
+       auto void q2(void);
+       void q2(void) { }
+}
+