PR 53796 Improve INQUIRE(RECL=...) handling

The current F2018 draft (N2137) specifies behavior of the RECL=
specifier in the INQUIRE statement, where it previously was left as
undefined. Namely:

- If the unit is not connected, RECL= should be given the value -1.
- If the unit is connected with stream access, RECL= should be given
  the value -2.

Further, as PR 53796 describes, the handling of RECL= is poor in other
ways as well. When the recl is set to the maximum possible
(GFC_INTEGER_8_HUGE / LLONG_MAX), which it does by default except for
preconnected units, and when INQUIRE(RECL=) is used with a 4 byte
integer, the value is truncated and the 4 byte value is thus
-1. Fixing this to generate an error is a lot of work, as currently
the truncation is done by the frontend, the library sees only an 8
byte value with no indication that the frontend is going to copy it to
a 4 byte one. Instead, this patch does a bit twiddling trick such that
the truncated 4 byte value is GFC_INTEGER_4_HUGE while still being
0.99999999 * GFC_INTEGER_8_HUGE which is large enough for all
practical purposes.

Finally, the patch removes GFORTRAN_DEFAULT_RECL which was used only
for preconnected units, and instead uses the same approach as describe
above.

Regtested on x86_64-pc-linux-gnu, Ok for trunk.

gcc/fortran/ChangeLog:

2017-11-28  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/53796
	* gfortran.texi: Remove mentions of GFORTRAN_DEFAULT_RECL.

libgfortran/ChangeLog:

2017-11-28  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/53796
	* io/inquire.c (inquire_via_unit): Set recl to -1 for unconnected
	units.
	* io/io.h (default_recl): New variable.
	* io/open.c (new_unit): Set recl to default_recl for sequential,
	-2 for stream access.
	* io/transfer.c (read_block_form): Test against default_recl
	instead of DEFAULT_RECL.
	(write_block): Likewise.
	* io/unit.c (init_units): Calculate max_offset, default_recl.
	* libgfortran.h (DEFAULT_RECL): Remove.
	* runtime/environ.c: Remove GFORTRAN_DEFAULT_RECL.

gcc/testsuite/ChangeLog:

2017-11-28  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/53796
	* gfortran.dg/inquire_recl_f2018.f90: New test.

From-SVN: r255215

1 files changed, 1 insertions, 7 deletions

diff --git a/libgfortran/libgfortran.h b/libgfortran/libgfortran.h
index 21ad5fc23fd..94aedc8c49f 100644
--- a/libgfortran/libgfortran.h
+++ b/libgfortran/libgfortran.h
@@ -511,7 +511,7 @@ typedef struct
   int separator_len;
   const char *separator;
 
-  int all_unbuffered, unbuffered_preconnected, default_recl;
+  int all_unbuffered, unbuffered_preconnected;
   int fpe, backtrace;
 }
 options_t;
@@ -577,12 +577,6 @@ extern char *filename;
 iexport_data_proto(filename);
 
 
-/* The default value of record length for preconnected units is defined
-   here. This value can be overriden by an environment variable.
-   Default value is 1 Gb.  */
-#define DEFAULT_RECL 1073741824
-
-
 #define CHARACTER2(name) \
               gfc_charlen_type name ## _len; \
               char * name