[gcc r13-4286] c: Propagate erroneous types to declaration specifiers [PR107805]

[gcc r13-4286] c: Propagate erroneous types to declaration specifiers [PR107805]

[Florian Weimer]

https://gcc.gnu.org/g:a42e39a7b974645d2820931357e99411fdb0beb6

commit r13-4286-ga42e39a7b974645d2820931357e99411fdb0beb6
Author: Florian Weimer <fweimer@redhat.com>
Date:   Thu Nov 24 11:00:54 2022 +0100

    c: Propagate erroneous types to declaration specifiers [PR107805]
    
    Without this change, finish_declspecs cannot tell that whether there
    was an erroneous type specified, or no type at all.  This may result
    in additional diagnostics for implicit ints, or missing diagnostics
    for multiple types.
    
            PR c/107805
    
    gcc/c/
            * c-decl.cc (declspecs_add_type): Propagate error_mark_bode
            from type to specs.
    
    gcc/testsuite/
            * gcc.dg/pr107805-1.c: New test.
            * gcc.dg/pr107805-2.c: Likewise.

Diff:
---
 gcc/c/c-decl.cc                   | 6 ++----
 gcc/testsuite/gcc.dg/pr107805-1.c | 5 +++++
 gcc/testsuite/gcc.dg/pr107805-2.c | 4 ++++
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 098e475f65d..4adb89e4aaf 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -12243,11 +12243,9 @@ declspecs_add_type (location_t loc, struct c_declspecs *specs,
     error_at (loc, "two or more data types in declaration specifiers");
   else if (TREE_CODE (type) == TYPE_DECL)
     {
-      if (TREE_TYPE (type) == error_mark_node)
-	; /* Allow the type to default to int to avoid cascading errors.  */
-      else
+      specs->type = TREE_TYPE (type);
+      if (TREE_TYPE (type) != error_mark_node)
 	{
-	  specs->type = TREE_TYPE (type);
 	  specs->decl_attr = DECL_ATTRIBUTES (type);
 	  specs->typedef_p = true;
 	  specs->explicit_signed_p = C_TYPEDEF_EXPLICITLY_SIGNED (type);
diff --git a/gcc/testsuite/gcc.dg/pr107805-1.c b/gcc/testsuite/gcc.dg/pr107805-1.c
new file mode 100644
index 00000000000..559b6a5586e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr107805-1.c
@@ -0,0 +1,5 @@
+/* { dg-do compile } */
+typedef int t;
+typedef struct { double a; int b; } t; /* { dg-error "conflicting types" } */
+t x; /* No warning here.  */
+
diff --git a/gcc/testsuite/gcc.dg/pr107805-2.c b/gcc/testsuite/gcc.dg/pr107805-2.c
new file mode 100644
index 00000000000..fa5fa4ce273
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr107805-2.c
@@ -0,0 +1,4 @@
+/* { dg-do compile } */
+typedef int t;
+typedef struct { double a; int b; } t; /* { dg-error "conflicting types" } */
+t char x; /* { dg-error "two or more data types" } */