[PATCH] c: Propagate erroneous types to declaration specifiers [PR107805]

[Florian Weimer <fweimer@redhat.com>]

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/pr107805-1.c: Likewise.

---
Note regarding testing: I boostrap with c,c++,lto on x86-64
(non-multlib) and diffed these .sum files:

gcc/testsuite/gcc/gcc.sum
gcc/testsuite/g++/g++.sum
x86_64-pc-linux-gnu/libgomp/testsuite/libgomp.sum
x86_64-pc-linux-gnu/libstdc++-v3/testsuite/libstdc++.sum
x86_64-pc-linux-gnu/libatomic/testsuite/libatomic.sum
x86_64-pc-linux-gnu/libitm/testsuite/libitm.sum

Apart from timestamps, the only differences I get is this change:

--- ./gcc/testsuite/gcc/gcc.sum 2022-11-22 05:45:33.813264761 -0500
+++ /tmp/b/build/./gcc/testsuite/gcc/gcc.sum    2022-11-22 06:39:10.667590185 -0500
@@ -83303,6 +83303,11 @@
 PASS: gcc.dg/pr107618.c  (test for bogus messages, line 9)
 PASS: gcc.dg/pr107618.c (test for excess errors)
 PASS: gcc.dg/pr107686.c (test for excess errors)
+PASS: gcc.dg/pr107805-1.c  (test for errors, line 3)
+PASS: gcc.dg/pr107805-1.c (test for excess errors)
+PASS: gcc.dg/pr107805-2.c  (test for errors, line 3)
+PASS: gcc.dg/pr107805-2.c  (test for errors, line 4)
+PASS: gcc.dg/pr107805-2.c (test for excess errors)
 PASS: gcc.dg/pr11459-1.c (test for excess errors)
 PASS: gcc.dg/pr11492.c  (test for bogus messages, line 8)
 PASS: gcc.dg/pr11492.c (test for excess errors)
@@ -190486,7 +190491,7 @@
 
                === gcc Summary ===
 
-# of expected passes           185932
+# of expected passes           185937
 # of unexpected failures       99
 # of unexpected successes      20
 # of expected failures         1484

So I think this means there are no test suite regressions.

Thanks,
Florian

 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" } */

base-commit: e4faee8d02ec5d65bf418612f7181823eb08c078