From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <sourceware-bugzilla@sourceware.org>
Received: by sourceware.org (Postfix, from userid 48)
	id C330E3858C41; Tue, 23 Jan 2024 20:27:01 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C330E3858C41
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org;
	s=default; t=1706041621;
	bh=wkQcnzAcWamXRYBpUV2i0rKk3z29wRr/+7wxM5gUqwY=;
	h=From:To:Subject:Date:From;
	b=Sws439U0lovXnurfsSPB/znQ9DgoY+6MJh02FII1yLJnPkYuZt/CfYmgHg5Ax+1WE
	 67Tbiumqf1MG/79PEas2yE5JnjbrAZ6LHaBGiNylrudChKuSbfH6kXKh4HMvoFMLfC
	 ArMbHWI76XHxxby3mzBDAx2Am2+Rg11dkA1wkcAs=
From: "vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug fortran/31282] New: [gdb/fortran] logical type doesn't match
 documentation of TYPE_CODE_BOOL
Date: Tue, 23 Jan 2024 20:27:01 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gdb
X-Bugzilla-Component: fortran
X-Bugzilla-Version: HEAD
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: vries at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at sourceware dot org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-31282-4717@http.sourceware.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://sourceware.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gdb-prs.sourceware.org>

https://sourceware.org/bugzilla/show_bug.cgi?id=3D31282

            Bug ID: 31282
           Summary: [gdb/fortran] logical type doesn't match documentation
                    of TYPE_CODE_BOOL
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: fortran
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

Consider the fortran type logical.

Here (
https://gcc.gnu.org/onlinedocs/gfortran/Internal-representation-of-LOGICAL-=
variables.html
) we read:
...
The Fortran standard does not specify how variables of LOGICAL type are
represented, beyond requiring that LOGICAL variables of default kind have t=
he
same storage size as default INTEGER and REAL variables. The GNU Fortran
internal representation is as follows.

A LOGICAL(KIND=3DN) variable is represented as an INTEGER(KIND=3DN) variabl=
e,
however, with only two permissible values: 1 for .TRUE. and 0 for .FALSE.. =
Any
other integer value results in undefined behavior.=20
...

OK, that's clear.  So how does this look in dwarf? Like so:
...
 <1><106>: Abbrev Number: 1 (DW_TAG_base_type)
    <107>   DW_AT_byte_size   : 4
    <108>   DW_AT_encoding    : 2       (boolean)
    <109>   DW_AT_name        : (indirect string, offset: 0x6): logical(kin=
d=3D4)
...

So, is there a clue to tell what the values of true/false are, other than
looking at the producer string and searching for "GNU Fortran"?

DW_AT_encoding ATE_boolean has the description of "true or false", so that
doesn't seem to help much.

However, internally in gdb, this type is mapped onto:
...
/* * Boolean type.  0 is false, 1 is true, and other values are
   non-boolean (e.g. FORTRAN "logical" used as unsigned int).  */
OP (TYPE_CODE_BOOL)
...

That doesn't seem correct.  If .TRUE. is, say 2, then using TYPE_CODE_BOOL
tells us to view it as non-boolean.

AFAICT this doesn't cause any trouble because there's special handling to d=
eal
with this discrepancy, for instance here in f-valprint.c:
...
          /* The Fortran standard doesn't specify how logical types are=20=
=20=20=20=20=20=20=20=20
             represented.  Different compilers use different non zero=20=20=
=20=20=20=20=20=20=20=20=20
             values to represent logical true.  */
          if (longval =3D=3D 0)
            gdb_puts (f_decorations.false_name, stream);
          else
            gdb_puts (f_decorations.true_name, stream);
...

--=20
You are receiving this mail because:
You are on the CC list for the bug.=