re PR fortran/20178 (COMPLEX function returns incompatible with g77)

gcc/fortran/
	PR fortran/20178
	* gfortran.h (gfc_option): Add flag_f2c.
	* invoke.texi: Document '-ff2c' command line option.  Adapt
	documentation for '-fno-second-underscore' and '-fno-underscoring'.
	* lang.opt (ff2c): New entry.
	* options.c (gfc-init_options): Set default calling convention
	to -fno-f2c.  Mark -fsecond-underscore unset.
	(gfc_post_options): Set -fsecond-underscore if not explicitly set
	by user.
	(handle_options): Set gfc_option.flag_f2c according to requested
	calling	convention.
	* trans-decl.c (gfc_get_extern_function_decl): Use special f2c
	intrinsics where necessary.
	(gfc_trans_deferred_vars): Change todo error to	assertion.
	* trans-expr.c (gfc_conv_variable): Dereference access
	to hidden result argument.
	(gfc_conv_function_call): Add hidden result argument to argument
	list if f2c calling conventions requested.  Slightly restructure
	tests.  Convert result of default REAL function to requested type
	if f2c calling conventions are used.  Dereference COMPLEX result
	if f2c cc are used.
	* trans-types.c (gfc_sym_type):  Return double for default REAL
	function if f2c cc are used.
	(gfc_return_by_reference): Slightly restructure logic.  Return
	COMPLEX by reference depending on calling conventions.
	(gfc_get_function_type): Correctly make hidden result argument a
	pass-by-reference argument for COMPLEX.  Remove old code which does
	this for derived types.
libgfortran/
	PR fortran/20178
	* Makefile.am (gfor_specific_src): Add 'intrinsics/f2c_intrinsics.F90'
	to dependencies.
	* Makefile.in: Regenerate.
	* intrinsics/f2c_specific.F90: New file.
gcc/testsuite/
	PR fortran/20178
	* gfortran.dg/f2c_1.f90, gfortran.dg/f2c_2.f90,
	gfortran.dg/f2c_3.f90: New tests.

From-SVN: r99544

12 files changed, 305 insertions, 32 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 1210aab..ee08d1f 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,34 @@
+2005-05-10  Tobias Schl"uter  <tobias.schlueter@physik.uni-muenchen.de>
+
+	PR fortran/20178
+	* gfortran.h (gfc_option): Add flag_f2c.
+	* invoke.texi: Document '-ff2c' command line option.  Adapt
+	documentation for '-fno-second-underscore' and '-fno-underscoring'.
+	* lang.opt (ff2c): New entry.
+	* options.c (gfc-init_options): Set default calling convention
+	to -fno-f2c.  Mark -fsecond-underscore unset.
+	(gfc_post_options): Set -fsecond-underscore if not explicitly set
+	by user.	
+	(handle_options): Set gfc_option.flag_f2c according to requested
+	calling	convention.
+	* trans-decl.c (gfc_get_extern_function_decl): Use special f2c
+	intrinsics where necessary.
+	(gfc_trans_deferred_vars): Change todo error to	assertion.
+	* trans-expr.c (gfc_conv_variable): Dereference access
+	to hidden result argument.
+	(gfc_conv_function_call): Add hidden result argument to argument
+	list if f2c calling conventions requested.  Slightly restructure
+	tests.  Convert result of default REAL function to requested type
+	if f2c calling conventions are used.  Dereference COMPLEX result
+	if f2c cc are used.
+	* trans-types.c (gfc_sym_type):  Return double for default REAL
+	function if f2c cc are used.
+	(gfc_return_by_reference): Slightly restructure logic.  Return
+	COMPLEX by reference depending on calling conventions.
+	(gfc_get_function_type): Correctly make hidden result argument a
+	pass-by-reference argument for COMPLEX.  Remove old code which does
+	this for derived types.
+
 2005-05-09  Tobias Schl"uter  <tobias.schlueter@physik.uni-muenchen.de>
 
 	* match.c (gfc_match_return): Only require space after keyword when
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 641e492..d17f388 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -1419,6 +1419,7 @@ typedef struct
   int flag_no_backend;
   int flag_pack_derived;
   int flag_repack_arrays;
+  int flag_f2c;
 
   int q_kind;
 
diff --git a/gcc/fortran/invoke.texi b/gcc/fortran/invoke.texi
index 22f20dc..5385bba 100644
--- a/gcc/fortran/invoke.texi
+++ b/gcc/fortran/invoke.texi
@@ -143,7 +143,7 @@ by type.  Explanations are in the following sections.
 @item Code Generation Options
 @xref{Code Gen Options,,Options for Code Generation Conventions}.
 @gccoptlist{
--fno-underscoring  -fno-second-underscore @gol
+-ff2c -fno-underscoring  -fsecond-underscore @gol
 -fbounds-check  -fmax-stack-var-size=@var{n} @gol
 -fpackderived  -frepack-arrays}
 @end table
@@ -518,8 +518,43 @@ it.
 
 
 @table @gcctabopt
-@cindex -fno-underscoring option
-@cindex options, -fno-underscoring
+@cindex @option{-ff2c} option
+@cindex options, @option{-ff2c}
+@item -ff2c
+@cindex calling convention
+@cindex @command{f2c} calling convention
+@cindex @command{g77} calling convention
+@cindex libf2c calling convention
+Generate code designed to be compatible with code generated
+by @command{g77} and @command{f2c}.
+
+The calling conventions used by @command{g77} (originally implemented
+in @command{f2c}) require functions that return type
+default @code{REAL} to actually return the C type @code{double}, and
+functions that return type @code{COMPLEX} to return the values via an
+extra argument in the calling sequence that points to where to
+store the return value.  Under the default GNU calling conventions, such
+functions simply return their results as they would in GNU
+C -- default @code{REAL} functions return the C type @code{float}, and
+@code{COMPLEX} functions return the GNU C type @code{complex}.
+Additionally, this option implies the @options{-fsecond-underscore}
+option, unless @options{-fno-second-underscore} is explicitly requested.
+
+This does not affect the generation of code that interfaces with
+the @command{libgfortran} library.
+
+@emph{Caution:} It is not a good idea to mix Fortran code compiled
+with @code{-ff2c} with code compiled with the default @code{-fno-f2c}
+calling conventions as, calling @code{COMPLEX} or default @code{REAL}
+functions between program parts which were compiled with different
+calling conventions will break at execution time.
+
+@emph{Caution:} This will break code which passes intrinsic functions
+of type default @code{REAL} or @code{COMPLEX} as actual arguments, as
+the library implementations use the @command{-fno-f2c} calling conventions.
+
+@cindex @option{-fno-underscoring option}
+@cindex options, @option{-fno-underscoring}
 @item -fno-underscoring
 @cindex underscore
 @cindex symbol names, underscores
@@ -528,16 +563,17 @@ it.
 Do not transform names of entities specified in the Fortran
 source file by appending underscores to them.
 
-With @option{-funderscoring} in effect, @command{gfortran} appends two
-underscores to names with underscores and one underscore to external names
-with no underscores.  (@command{gfortran} also appends two underscores to
-internal names with underscores to avoid naming collisions with external
-names.  The @option{-fno-second-underscore} option disables appending of the
-second underscore in all cases.)
+With @option{-funderscoring} in effect, @command{gfortran} appends one
+underscore to external names with no underscores.
 
 This is done to ensure compatibility with code produced by many
-UNIX Fortran compilers, including @command{f2c} which perform the
-same transformations.
+UNIX Fortran compilers.
+
+@emph{Caution}: The default behavior of @command{gfortran} is
+incompatible with @command{f2c} and @command{g77}, please use the
+@option{-ff2c} and @option{-fsecond-underscore} options if you want
+object files compiled with @option{gfortran} to be compatible with
+object code created with these tools.
 
 Use of @option{-fno-underscoring} is not recommended unless you are
 experimenting with issues such as integration of (GNU) Fortran into
@@ -593,22 +629,31 @@ in the source, even if the names as seen by the linker are mangled to
 prevent accidental linking between procedures with incompatible
 interfaces.
 
-@cindex -fno-second-underscore option
-@cindex options, -fno-second-underscore
-@item -fno-second-underscore
+@cindex @option{-fsecond-underscore option}
+@cindex options, @option{-fsecond-underscore}
+@item -fsecond-underscore
 @cindex underscore
 @cindex symbol names, underscores
 @cindex transforming symbol names
 @cindex symbol names, transforming
-Do not append a second underscore to names of entities specified
-in the Fortran source file.
+@cindex @command{f2c} calling convention
+@cindex @command{g77} calling convention
+@cindex libf2c calling convention
+By default, @command{gfortran} appends an underscore to external
+names.  If this option is used @command{gfortran} appends two
+underscores to names with underscores and one underscore to external names
+with no underscores.  (@command{gfortran} also appends two underscores to
+internal names with underscores to avoid naming collisions with external
+names.
 
 This option has no effect if @option{-fno-underscoring} is
-in effect.
+in effect.  It is implied by the @option{-ff2c} option.
 
 Otherwise, with this option, an external name such as @samp{MAX_COUNT}
 is implemented as a reference to the link-time external symbol
-@samp{max_count_}, instead of @samp{max_count__}.
+@samp{max_count__}, instead of @samp{max_count_}.  This is required
+for compatibility with @command{g77} and @command{f2c}, and is implied
+by use of the @option{-ff2c} option.
 
 
 @cindex -fbounds-check option
diff --git a/gcc/fortran/lang.opt b/gcc/fortran/lang.opt
index 645b3e9..d1ca5f0 100644
--- a/gcc/fortran/lang.opt
+++ b/gcc/fortran/lang.opt
@@ -89,6 +89,10 @@ fdump-parse-tree
 F95
 Display the code tree after parsing.
 
+ff2c
+F95
+Use f2c calling convention.
+
 ffixed-form
 F95
 Assume that the source file is fixed form
diff --git a/gcc/fortran/options.c b/gcc/fortran/options.c
index 21fb0a8..2603caa 100644
--- a/gcc/fortran/options.c
+++ b/gcc/fortran/options.c
@@ -62,7 +62,8 @@ gfc_init_options (unsigned int argc ATTRIBUTE_UNUSED,
   gfc_option.flag_default_real = 0;
   gfc_option.flag_dollar_ok = 0;
   gfc_option.flag_underscoring = 1;
-  gfc_option.flag_second_underscore = 1;
+  gfc_option.flag_f2c = 0;
+  gfc_option.flag_second_underscore = -1;
   gfc_option.flag_implicit_none = 0;
   gfc_option.flag_max_stack_var_size = 32768;
   gfc_option.flag_module_access_private = 0;
@@ -113,6 +114,12 @@ gfc_post_options (const char **pfilename)
   if (pedantic && (gfc_option.allow_std & GFC_STD_GNU) != 0)
     gfc_option.warn_std |= GFC_STD_GNU;
 
+  /* If the user didn't explicitly specify -f(no)-second-underscore we
+     use it if we're trying to be compatible with f2c, and not
+     otherwise.  */
+  if (gfc_option.flag_second_underscore == -1)
+    gfc_option.flag_second_underscore = gfc_option.flag_f2c;
+
   return false;
 }
 
@@ -214,6 +221,10 @@ gfc_handle_option (size_t scode, const char *arg, int value)
       gfc_option.warn_unused_labels = value;
       break;
 
+    case OPT_ff2c:
+      gfc_option.flag_f2c = value;
+      break;
+
     case OPT_fdollar_ok:
       gfc_option.flag_dollar_ok = value;
       break;
diff --git a/gcc/fortran/trans-decl.c b/gcc/fortran/trans-decl.c
index d5075b9..3d89eff 100644
--- a/gcc/fortran/trans-decl.c
+++ b/gcc/fortran/trans-decl.c
@@ -901,7 +901,7 @@ gfc_get_extern_function_decl (gfc_symbol * sym)
   gfc_expr e;
   gfc_intrinsic_sym *isym;
   gfc_expr argexpr;
-  char s[GFC_MAX_SYMBOL_LEN];
+  char s[GFC_MAX_SYMBOL_LEN + 13]; /* "f2c_specific" and '\0'.  */
   tree name;
   tree mangled_name;
 
@@ -937,7 +937,18 @@ gfc_get_extern_function_decl (gfc_symbol * sym)
 	  gcc_assert (isym->formal->next->next == NULL);
 	  isym->resolve.f2 (&e, &argexpr, NULL);
 	}
-      sprintf (s, "specific%s", e.value.function.name);
+
+      if (gfc_option.flag_f2c
+	  && ((e.ts.type == BT_REAL && e.ts.kind == gfc_default_real_kind)
+	      || e.ts.type == BT_COMPLEX))
+	{
+	  /* Specific which needs a different implementation if f2c
+	     calling conventions are used.  */
+	  sprintf (s, "f2c_specific%s", e.value.function.name);
+	}
+      else
+	sprintf (s, "specific%s", e.value.function.name);
+
       name = get_identifier (s);
       mangled_name = name;
     }
@@ -2030,7 +2041,8 @@ gfc_trans_deferred_vars (gfc_symbol * proc_sym, tree fnbody)
 	    fnbody = gfc_trans_dummy_character (proc_sym->ts.cl, fnbody);
 	}
       else
-	gfc_todo_error ("Deferred non-array return by reference");
+	gcc_assert (gfc_option.flag_f2c
+		    && proc_sym->ts.type == BT_COMPLEX);
     }
 
   for (sym = proc_sym->tlink; sym != proc_sym; sym = sym->tlink)
diff --git a/gcc/fortran/trans-expr.c b/gcc/fortran/trans-expr.c
index caf3d75..35c3f12 100644
--- a/gcc/fortran/trans-expr.c
+++ b/gcc/fortran/trans-expr.c
@@ -362,6 +362,13 @@ gfc_conv_variable (gfc_se * se, gfc_expr * expr)
 	  && !sym->attr.dimension)
 	se->expr = gfc_build_indirect_ref (se->expr);
 
+      /* Dereference scalar hidden result.  */
+      if (gfc_option.flag_f2c 
+	  && (sym->attr.function || sym->attr.result)
+	  && sym->ts.type == BT_COMPLEX
+	  && !sym->attr.dimension)
+	se->expr = gfc_build_indirect_ref (se->expr);
+
       /* Dereference pointer variables.  */
       if ((sym->attr.pointer || sym->attr.allocatable)
 	  && (sym->attr.dummy
@@ -1138,7 +1145,13 @@ gfc_conv_function_call (gfc_se * se, gfc_symbol * sym,
 				      convert (gfc_charlen_type_node, len));
 	}
       else
-	gcc_unreachable ();
+	{
+	  gcc_assert (gfc_option.flag_f2c && sym->ts.type == BT_COMPLEX);
+
+	  type = gfc_get_complex_type (sym->ts.kind);
+	  var = gfc_build_addr_expr (NULL, gfc_create_var (type, "cmplx"));
+	  arglist = gfc_chainon_list (arglist, var);
+	}
     }
 
   formal = sym->formal;
@@ -1240,14 +1253,25 @@ gfc_conv_function_call (gfc_se * se, gfc_symbol * sym,
   se->expr = build3 (CALL_EXPR, TREE_TYPE (fntype), se->expr,
 		     arglist, NULL_TREE);
 
+  if (sym->result)
+    sym = sym->result;
+
   /* If we have a pointer function, but we don't want a pointer, e.g.
      something like
         x = f()
      where f is pointer valued, we have to dereference the result.  */
-  if (!se->want_pointer && !byref
-      && (sym->attr.pointer || (sym->result && sym->result->attr.pointer)))
+  if (!se->want_pointer && !byref && sym->attr.pointer)
     se->expr = gfc_build_indirect_ref (se->expr);
 
+  /* f2c calling conventions require a scalar default real function to
+     return a double precision result.  Convert this back to default
+     real.  We only care about the cases that can happen in Fortran 77.
+  */
+  if (gfc_option.flag_f2c && sym->ts.type == BT_REAL
+      && sym->ts.kind == gfc_default_real_kind
+      && !sym->attr.always_explicit)
+    se->expr = fold_convert (gfc_get_real_type (sym->ts.kind), se->expr);
+
   /* A pure function may still have side-effects - it may modify its
      parameters.  */
   TREE_SIDE_EFFECTS (se->expr) = 1;
@@ -1282,7 +1306,10 @@ gfc_conv_function_call (gfc_se * se, gfc_symbol * sym,
 	      se->string_length = len;
 	    }
 	  else
-	    gcc_unreachable ();
+	    {
+	      gcc_assert (sym->ts.type == BT_COMPLEX && gfc_option.flag_f2c);
+	      se->expr = gfc_build_indirect_ref (var);
+	    }
 	}
     }
 }
diff --git a/gcc/fortran/trans-types.c b/gcc/fortran/trans-types.c
index d63917a..b2c5169 100644
--- a/gcc/fortran/trans-types.c
+++ b/gcc/fortran/trans-types.c
@@ -1272,6 +1272,18 @@ gfc_sym_type (gfc_symbol * sym)
     sym = sym->result;
 
   type = gfc_typenode_for_spec (&sym->ts);
+  if (gfc_option.flag_f2c
+      && sym->attr.function
+      && sym->ts.type == BT_REAL
+      && sym->ts.kind == gfc_default_real_kind
+      && !sym->attr.always_explicit)
+    {
+      /* Special case: f2c calling conventions require that (scalar) 
+	 default REAL functions return the C type double instead.  */
+      sym->ts.kind = gfc_default_double_kind;
+      type = gfc_typenode_for_spec (&sym->ts);
+      sym->ts.kind = gfc_default_real_kind;
+    }
 
   if (sym->attr.dummy && !sym->attr.function)
     byref = 1;
@@ -1453,19 +1465,29 @@ gfc_get_derived_type (gfc_symbol * derived)
 int
 gfc_return_by_reference (gfc_symbol * sym)
 {
+  gfc_symbol *result;
+
   if (!sym->attr.function)
     return 0;
 
-  if (sym->result)
-    sym = sym->result;
+  result = sym->result ? sym->result : sym;
 
-  if (sym->attr.dimension)
+  if (result->attr.dimension)
     return 1;
 
-  if (sym->ts.type == BT_CHARACTER)
+  if (result->ts.type == BT_CHARACTER)
     return 1;
 
-  /* Possibly return complex numbers by reference for g77 compatibility.  */
+  /* Possibly return complex numbers by reference for g77 compatibility.
+     We don't do this for calls to intrinsics (as the library uses the
+     -fno-f2c calling convention), nor for calls to functions which always
+     require an explicit interface, as no compatibility problems can
+     arise there.  */
+  if (gfc_option.flag_f2c
+      && result->ts.type == BT_COMPLEX
+      && !sym->attr.intrinsic && !sym->attr.always_explicit)
+    return 1;
+  
   return 0;
 }
 
@@ -1551,7 +1573,7 @@ gfc_get_function_type (gfc_symbol * sym)
 	gfc_conv_const_charlen (arg->ts.cl);
 
       type = gfc_sym_type (arg);
-      if (arg->ts.type == BT_DERIVED
+      if (arg->ts.type == BT_COMPLEX
 	  || arg->attr.dimension
 	  || arg->ts.type == BT_CHARACTER)
 	type = build_reference_type (type);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 55363ea..7065773 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2005-05-10  Tobias Schl"uter  <tobias.schlueter@physik.uni-muenchen.de>
+
+	PR fortran/20178
+	* gfortran.dg/f2c_1.f90, gfortran.dg/f2c_2.f90,
+	gfortran.dg/f2c_3.f90: New tests.
+
 2005-05-10  Diego Novillo  <dnovillo@redhat.com>
 
 	* gcc.c-torture/compile/20050510-1.c: New test.
diff --git a/gcc/testsuite/gfortran.dg/f2c_1.f90 b/gcc/testsuite/gfortran.dg/f2c_1.f90
new file mode 100644
index 0000000..9f45d05
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/f2c_1.f90
@@ -0,0 +1,73 @@
+! Make sure the f2c calling conventions work
+! { dg-do run }
+! { dg-options "-ff2c" }
+
+function f(x)
+  f = x
+end function f
+
+complex function c(a,b)
+  c = cmplx (a,b)
+end function c
+
+double complex function d(e,f)
+  double precision e, f
+  d = cmplx (e, f, kind(d))
+end function d
+
+subroutine test_with_interface()
+  interface
+     real function f(x)
+       real::x
+     end function f
+  end interface
+
+  interface
+     complex function c(a,b)
+       real::a,b
+     end function c
+  end interface
+
+  interface
+     double complex function d(e,f)
+       double precision::e,f
+     end function d
+  end interface
+  
+  double precision z, w
+
+  x = 8.625
+  if (x /= f(x)) call abort ()
+  y = f(x)
+  if (x /= y) call abort ()
+
+  a = 1.
+  b = -1.
+  if (c(a,b) /= cmplx(a,b)) call abort ()
+
+  z = 1.
+  w = -1.
+  if (d(z,w) /= cmplx(z,w, kind(z))) call abort ()
+end subroutine test_with_interface
+
+external f, c, d
+real f
+complex c
+double complex d
+double precision z, w
+
+x = 8.625
+if (x /= f(x)) call abort ()
+y = f(x)
+if (x /= y) call abort ()
+
+a = 1.
+b = -1.
+if (c(a,b) /= cmplx(a,b)) call abort ()
+
+z = 1.
+w = -1.
+if (d(z,w) /= cmplx(z,w, kind(z))) call abort ()
+
+call test_with_interface ()
+end
diff --git a/gcc/testsuite/gfortran.dg/f2c_2.f90 b/gcc/testsuite/gfortran.dg/f2c_2.f90
new file mode 100644
index 0000000..82ab5f0
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/f2c_2.f90
@@ -0,0 +1,23 @@
+! Some basic testing that calls to the library still work correctly with
+! -ff2c
+!
+! Once the library has support for f2c calling conventions (i.e. passing
+! a REAL*4 or COMPLEX-valued intrinsic as procedure argument works), we
+! can simply add -ff2c to the list of options to cycle through, and get
+! complete coverage.  As of 2005-03-05 this doesn't work.
+! { dg-do run }
+! { dg-options "-ff2c" }
+
+complex c
+double complex d
+
+x = 2.
+if ((sqrt(x) - 1.41)**2 > 1.e-4) call abort ()
+x = 1.
+if ((atan(x) - 3.14/4) ** 2 > 1.e-4) call abort ()
+c = (-1.,0.)
+if (sqrt(c) /= (0., 1.)) call abort ()
+d = c
+if (sqrt(d) /= (0._8, 1._8)) call abort ()
+end
+ 
diff --git a/gcc/testsuite/gfortran.dg/f2c_3.f90 b/gcc/testsuite/gfortran.dg/f2c_3.f90
new file mode 100644
index 0000000..6854457
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/f2c_3.f90
@@ -0,0 +1,18 @@
+! { dg-do run }
+! { dg-options "-ff2c" }
+! Verifies that internal functions are not broken by f2c calling conventions
+program test
+  real, target :: f
+  real, pointer :: q
+  real :: g
+  f = 1.0
+  q=>f
+  g = foo(q)
+  if (g .ne. 1.0) call abort
+contains
+function foo (p)
+  real, pointer :: foo
+  real, pointer :: p
+  foo => p
+end function
+end program