Fortran: ALLOCATE of fixed-length CHARACTER with SOURCE/MOLD [PR113793]

F2008 requires for ALLOCATE with SOURCE= or MOLD= specifier that the kind
type parameters of allocate-object and source-expr have the same values.
Add compile-time diagnostics for different character length and a runtime
check (under -fcheck=bounds).  Use length from allocate-object to prevent
heap corruption and to allow string padding or truncation on assignment.

gcc/fortran/ChangeLog:

	PR fortran/113793
	* resolve.cc (resolve_allocate_expr): Reject ALLOCATE with SOURCE=
	or MOLD= specifier for unequal length.
	* trans-stmt.cc (gfc_trans_allocate): If an allocatable character
	variable has fixed length, use it and do not use the source length.
	With bounds-checking enabled, add a runtime check for same length.

gcc/testsuite/ChangeLog:

	PR fortran/113793
	* gfortran.dg/allocate_with_source_29.f90: New test.
	* gfortran.dg/allocate_with_source_30.f90: New test.
	* gfortran.dg/allocate_with_source_31.f90: New test.

5 files changed, 179 insertions, 4 deletions

diff --git a/gcc/fortran/resolve.cc b/gcc/fortran/resolve.cc
index 4cbf7186..6b3e5ba 100644
--- a/gcc/fortran/resolve.cc
+++ b/gcc/fortran/resolve.cc
@@ -8278,6 +8278,16 @@ resolve_allocate_expr (gfc_expr *e, gfc_code *code, bool *array_alloc_wo_spec)
 	  goto failure;
 	}
 
+      /* Check F2008:C639: "Corresponding kind type parameters of
+	 allocate-object and source-expr shall have the same values."  */
+      if (e->ts.type == BT_CHARACTER
+	  && !e->ts.deferred
+	  && e->ts.u.cl->length
+	  && code->expr3->ts.type == BT_CHARACTER
+	  && !gfc_check_same_strlen (e, code->expr3, "ALLOCATE with "
+				     "SOURCE= or MOLD= specifier"))
+	    goto failure;
+
       /* Check TS18508, C702/C703.  */
       if (code->expr3->ts.type == BT_DERIVED
 	  && ((codimension && gfc_expr_attr (code->expr3).event_comp)
diff --git a/gcc/fortran/trans-stmt.cc b/gcc/fortran/trans-stmt.cc
index 7997c16..c34e0b4 100644
--- a/gcc/fortran/trans-stmt.cc
+++ b/gcc/fortran/trans-stmt.cc
@@ -6829,10 +6829,26 @@ gfc_trans_allocate (gfc_code * code, gfc_omp_namelist *omp_allocate)
 	     in the array is needed, which is the product of the len and
 	     esize for char arrays.  For unlimited polymorphics len can be
 	     zero, therefore take the maximum of len and one.  */
+	  tree lhs_len;
+
+	  /* If an allocatable character variable has fixed length, use it.
+	     Otherwise use source length.  As different lengths are not
+	     allowed by the standard, generate a runtime check.  */
+	  if (expr->ts.type == BT_CHARACTER && !expr->ts.deferred)
+	    {
+	      gfc_trans_same_strlen_check ("ALLOCATE with SOURCE= or MOLD=",
+					   &code->expr3->where,
+					   se.string_length, expr3_len,
+					   &block);
+	      lhs_len = fold_convert (TREE_TYPE (expr3_len), se.string_length);
+	    }
+	  else
+	    lhs_len = expr3_len;
+
 	  tmp = fold_build2_loc (input_location, MAX_EXPR,
 				 TREE_TYPE (expr3_len),
-				 expr3_len, fold_convert (TREE_TYPE (expr3_len),
-							  integer_one_node));
+				 lhs_len, fold_convert (TREE_TYPE (expr3_len),
+							integer_one_node));
 	  tmp = fold_build2_loc (input_location, MULT_EXPR,
 				 TREE_TYPE (expr3_esize), expr3_esize,
 				 fold_convert (TREE_TYPE (expr3_esize), tmp));
@@ -6877,10 +6893,22 @@ gfc_trans_allocate (gfc_code * code, gfc_omp_namelist *omp_allocate)
 	     allocate.
 
 	     expr3_len is set when expr3 is an unlimited polymorphic
-	     object or a deferred length string.  */
+	     object or a deferred length string.
+
+	     If an allocatable character variable has fixed length, use it.
+	     Otherwise use source length.  As different lengths are not
+	     allowed by the standard, a runtime check was inserted
+	     above.  */
 	  if (expr3_len != NULL_TREE)
 	    {
-	      tmp = fold_convert (TREE_TYPE (expr3_esize), expr3_len);
+	      tree lhs_len;
+	      if (expr->ts.type == BT_CHARACTER && !expr->ts.deferred)
+		lhs_len = fold_convert (TREE_TYPE (expr3_len),
+					se.string_length);
+	      else
+		lhs_len = expr3_len;
+
+	      tmp = fold_convert (TREE_TYPE (expr3_esize), lhs_len);
 	      tmp = fold_build2_loc (input_location, MULT_EXPR,
 				     TREE_TYPE (expr3_esize),
 				      expr3_esize, tmp);
diff --git a/gcc/testsuite/gfortran.dg/allocate_with_source_29.f90 b/gcc/testsuite/gfortran.dg/allocate_with_source_29.f90
new file mode 100644
index 0000000..b3d4c8a
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/allocate_with_source_29.f90
@@ -0,0 +1,48 @@
+! { dg-do compile }
+! { dg-options "-std=f2008" }
+! PR fortran/113793
+!
+! Static checks of string length for ALLOCATE with SOURCE= or MOLD=
+
+program p
+  implicit none
+  character(kind=1,len=8), allocatable :: a(:), d, b(:,:)
+  character(kind=4,len=6), allocatable :: c(:), e, f(:,:)
+  character(kind=1,len=2)              :: c1 = "xx"
+  character(kind=1,len=8)              :: c2 = "yy"
+  character(kind=4,len=6)              :: c3 = 4_"ww"
+  character(kind=4,len=3)              :: c4 = 4_"zz"
+
+  ALLOCATE (a(1),source=  "a")       ! { dg-error "Unequal character lengths .8/1. " }
+  ALLOCATE (a(2),mold  =  "bb")      ! { dg-error "Unequal character lengths .8/2. " }
+  ALLOCATE (c(3),source=4_"yyy")     ! { dg-error "Unequal character lengths .6/3. " }
+  ALLOCATE (c(4),mold  =4_"zzzz")    ! { dg-error "Unequal character lengths .6/4. " }
+  ALLOCATE (d,   source=  "12345")   ! { dg-error "Unequal character lengths .8/5. " }
+  ALLOCATE (d,   source=  "12345678")
+  ALLOCATE (d,   mold  =  "123456")  ! { dg-error "Unequal character lengths .8/6. " }
+  ALLOCATE (e,   source=4_"654321")
+  ALLOCATE (e,   mold  =4_"7654321") ! { dg-error "Unequal character lengths .6/7. " }
+  ALLOCATE (a(5),source=c1)          ! { dg-error "Unequal character lengths .8/2. " }
+  ALLOCATE (a(6),mold  =c1)          ! { dg-error "Unequal character lengths .8/2. " }
+  ALLOCATE (c(7),source=c4)          ! { dg-error "Unequal character lengths .6/3. " }
+  ALLOCATE (c(8),mold  =c4)          ! { dg-error "Unequal character lengths .6/3. " }
+  ALLOCATE (a,source=[c1,c1,c1])     ! { dg-error "Unequal character lengths .8/2. " }
+  ALLOCATE (a,source=[c2,c2,c2])
+  ALLOCATE (c,source=[c3,c3])
+  ALLOCATE (c,source=[c4,c4])        ! { dg-error "Unequal character lengths .6/3. " }
+  ALLOCATE (d,source=c1)             ! { dg-error "Unequal character lengths .8/2. " }
+  ALLOCATE (e,source=c4)             ! { dg-error "Unequal character lengths .6/3. " }
+  ALLOCATE (b,source=reshape([c1],[1,1])) ! { dg-error "Unequal character lengths .8/2. " }
+  ALLOCATE (b,source=reshape([c2],[1,1]))
+  ALLOCATE (f,source=reshape([c3],[1,1]))
+  ALLOCATE (f,source=reshape([c4],[1,1])) ! { dg-error "Unequal character lengths .6/3. " }
+contains
+  subroutine foo (s)
+    character(*), intent(in) :: s
+    character(len=8), allocatable :: f(:), g
+    ALLOCATE (f(3), source=s)
+    ALLOCATE (d,    source=s)
+    ALLOCATE (f(3), mold=s)
+    ALLOCATE (d,    mold=s)
+  end
+end
diff --git a/gcc/testsuite/gfortran.dg/allocate_with_source_30.f90 b/gcc/testsuite/gfortran.dg/allocate_with_source_30.f90
new file mode 100644
index 0000000..f8a71d1
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/allocate_with_source_30.f90
@@ -0,0 +1,51 @@
+! { dg-do run }
+! { dg-additional-options "-std=f2008 -fcheck=bounds -g -fdump-tree-original" }
+! { dg-output "At line 43 .*" }
+! { dg-shouldfail "Unequal character lengths .3/2. in ALLOCATE with SOURCE= or MOLD=" }
+!
+! PR fortran/113793
+!
+! Test runtime checks of string length for ALLOCATE with SOURCE= or MOLD=
+
+program p
+  implicit none
+  character(kind=1,len=2) :: c1 =   "xx"
+  character(kind=1,len=8) :: c2 =   "yy"
+  character(kind=4,len=6) :: c3 = 4_"ww"
+  call sub1 (len (c2), c2)
+  call sub4 (len (c3), c3)
+  call test (len (c1) + 1, c1)
+contains
+  subroutine sub1 (n, s)
+    integer,      intent(in) :: n
+    character(*), intent(in) :: s
+    character(len=8), allocatable :: f(:), g
+    character(len=n), allocatable :: h(:), j
+    ALLOCATE (f(7), source=s)
+    ALLOCATE (g,    source=s)
+    ALLOCATE (h(5), mold=s)
+    ALLOCATE (j,    mold=s)
+  end
+  subroutine sub4 (n, s)
+    integer,                 intent(in) :: n
+    character(kind=4,len=*), intent(in) :: s
+    character(kind=4,len=6), allocatable :: f(:), g
+    character(kind=4,len=n), allocatable :: h(:), j
+    ALLOCATE (f(3), source=s)
+    ALLOCATE (g,    source=s)
+    ALLOCATE (h(5), mold=s)
+    ALLOCATE (j,    mold=s)
+  end
+  subroutine test (n, s)
+    integer,      intent(in) :: n
+    character(*), intent(in) :: s
+    character(len=n), allocatable :: str
+    ALLOCATE (str, source=s)
+  end
+end
+
+! { dg-final { scan-tree-dump-times "__builtin_malloc .72.;" 1 "original" } }
+! { dg-final { scan-tree-dump-times "__builtin_malloc .24.;" 1 "original" } }
+! { dg-final { scan-tree-dump-times "__builtin_malloc .56.;" 1 "original" } }
+! { dg-final { scan-tree-dump-times "__builtin_malloc .8.;" 1 "original" } }
+! { dg-final { scan-tree-dump-times "ALLOCATE with SOURCE= or MOLD=" 9 "original" } }
diff --git a/gcc/testsuite/gfortran.dg/allocate_with_source_31.f90 b/gcc/testsuite/gfortran.dg/allocate_with_source_31.f90
new file mode 100644
index 0000000..50c6098
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/allocate_with_source_31.f90
@@ -0,0 +1,38 @@
+! { dg-do run }
+! { dg-additional-options "-std=gnu -fcheck=no-bounds" }
+!
+! PR fortran/113793
+!
+! Test extension for ALLOCATE with SOURCE= or MOLD= that strings
+! are truncated or padded and no memory corruption occurs
+
+program p
+  implicit none
+  call test_pad   (8, "12345")
+  call test_trunc (6, "123456789")
+contains
+  subroutine test_pad (n, s)
+    integer,      intent(in) :: n
+    character(*), intent(in) :: s
+    character(len=n), allocatable :: a(:), b(:,:)
+    if (len (s) >= n) stop 111
+    ALLOCATE (a(100),source=s)
+    ALLOCATE (b(5,6),source=s)
+!   print *, ">", a(42), "<"
+!   print *, ">", b(3,4), "<"
+    if (a(42)  /= s) stop 1
+    if (b(3,4) /= s) stop 2
+  end
+  subroutine test_trunc (n, s)
+    integer,      intent(in) :: n
+    character(*), intent(in) :: s
+    character(len=n), allocatable :: a(:), b(:,:)
+    if (len (s) <= n) stop 222
+    ALLOCATE (a(100),source=s)
+    ALLOCATE (b(5,6),source=s)
+!   print *, ">", a(42), "<"
+!   print *, ">", b(3,4), "<"
+    if (a(42)  /= s(1:n)) stop 3
+    if (b(3,4) /= s(1:n)) stop 4
+  end
+end