From 06c1d0a96544640c7b1485fe977337ef1572ac91 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Sun, 11 Dec 2022 23:24:03 +0100
Subject: [PATCH] Fortran: improve checking of assumed size array spec
 [PR102180]

gcc/fortran/ChangeLog:

	PR fortran/102180
	* array.cc (match_array_element_spec): Add check for bad
	assumed-implied-spec.
	(gfc_match_array_spec): Reorder logic so that a first bad array
	element spec may trigger an error.

gcc/testsuite/ChangeLog:

	PR fortran/102180
	* gfortran.dg/pr102180.f90: New test.
---
 gcc/fortran/array.cc                   | 12 ++++++++++--
 gcc/testsuite/gfortran.dg/pr102180.f90 | 19 +++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pr102180.f90

diff --git a/gcc/fortran/array.cc b/gcc/fortran/array.cc
index bbdb5b392fc..9c1d55fa8cc 100644
--- a/gcc/fortran/array.cc
+++ b/gcc/fortran/array.cc
@@ -488,6 +488,14 @@ match_array_element_spec (gfc_array_spec *as)
       return AS_ASSUMED_SIZE;
     }

+  /* F2018:R821: "assumed-implied-spec  is  [ lower-bound : ] *".  */
+  if (gfc_match (" : * ") == MATCH_YES)
+    {
+      gfc_error ("A lower bound must precede colon in "
+		 "assumed size array specification at %C");
+      return AS_UNKNOWN;
+    }
+
   if (gfc_match_char (':') == MATCH_YES)
     return AS_DEFERRED;

@@ -591,6 +599,8 @@ gfc_match_array_spec (gfc_array_spec **asp, bool match_dim, bool match_codim)
     {
       as->rank++;
       current_type = match_array_element_spec (as);
+      if (current_type == AS_UNKNOWN)
+	goto cleanup;

       /* Note that current_type == AS_ASSUMED_SIZE for both assumed-size
 	 and implied-shape specifications.  If the rank is at least 2, we can
@@ -600,8 +610,6 @@ gfc_match_array_spec (gfc_array_spec **asp, bool match_dim, bool match_codim)

       if (as->rank == 1)
 	{
-	  if (current_type == AS_UNKNOWN)
-	    goto cleanup;
 	  as->type = current_type;
 	}
       else
diff --git a/gcc/testsuite/gfortran.dg/pr102180.f90 b/gcc/testsuite/gfortran.dg/pr102180.f90
new file mode 100644
index 00000000000..cbf3e7299e7
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr102180.f90
@@ -0,0 +1,19 @@
+! { dg-do compile }
+! { dg-options "-fcoarray=lib" }
+! PR fortran/102180 - Improve checking of assumed size array spec
+
+subroutine s(x,y)
+  real :: x(0:*) ! legal
+  real :: y[0:*] ! legal
+end
+
+subroutine t(x,y)
+  real :: x(:*) ! { dg-error "A lower bound must precede colon" }
+  real :: y[:*] ! { dg-error "A lower bound must precede colon" }
+end
+
+subroutine u(x,y,z)
+  real :: x(2,*)
+  real :: y(2,2:*)
+  real :: z(2,:*) ! { dg-error "A lower bound must precede colon" }
+end
--
2.35.3