bug report for g77 (F77 fortran compiler)

[Tim Prince]

AFAIK g77 is not intended to provide full support for the "f66"
standard, which was the only version of the Fortran standard to
support "extended range of a DO"  cf ISO 1539-1980(E) p. A-2
paragraph (7).  Yes, the diagnostic level and support for the
undesirable (and now, for 10 years, officially obsolescent)
assigned go to is weak.

----- Original Message -----
From: "Jerzy Tarasiuk" <jt@japc50.fuw.edu.pl>
To: <gcc-bugs@gcc.gnu.org>
Cc: <jt@fuw.edu.pl>
Sent: Tuesday, May 09, 2000 10:25 AM
Subject: bug report for g77 (F77 fortran compiler)


> Hello, here is a program which shows the bug.
>
> The compiler version: egcs-g77.1.1.2 (details on end).
>
> Problem: DO has hidden variable which causes it to behave
> differently from Fortran standard - terminate the DO loop
> prematurely if another loop was executed during the time;
> the variable keeps remaing count of loop repeats;
> this occurs when jump is done outside the loop range and
> then back into the loop (such a construction is allowed
> by the standard). Also, the compiler shows warning or
> error (depends on order of instructions) when such a jump
> is used (the warning is not shown if it is assigned goto).
>
> The program worked OK with every other compiler I seen.
>
> Jerzy Tarasiuk  <jt@fuw.edu.pl>
>
> ----------------------------------------------------------
>
> program dotest
>
> C**** DOTEST - show a bug of 'DO' in Linux F77 compiler.
> C
> C Jerzy Tarasiuk 09 May 2000
> C
> k=0
> l=5
> i=-1
> C without the following ASSIGN result is the same,
> C but the compiler issues warning in spite it is valid
> C in FORTRAN to jump outside DO loop and back jump into it.
> assign 4 to j
> do 4 i=1,l
> C the following WRITE is executed 2 times, the DO loop ends
> C in spite the value of L is 5 - this is the _BUG_ of F77!
> write(*,1004) 'l',i,k,l
> goto 41
>  4 continue
> write(*,1004) 'e',i,k,l
> stop
> C can put here instructions change value of K only, the K=1
> C is used twice to make final value of K independent of I
> C but the result does not depend on the change.
>  41 if(i.eq.1) goto j
> C for first pass of DO 4 the IF condition is met and return
> C to DO 4 loop is done in the line above; for next pass the
> C condition is missed and the DO loop below is executed;
> C the only result of the loop should be changing of K which
> C is irrelevant, but it has also hidden side effect which
> C causes the bug: internal loop counter is set to -1, and
> C the DO 4 loop is terminated on begin of next pass.
> do 42 k=1,i
>  42 continue
> goto j
>  1004 format(1x,a1,3h i=,i2,3h k=,i2,3h l=,i2)
> end
>
> ------------------------------------------------------------
>
> $ g77 --verbose
>
> g77 version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)
(from FSF-g77 version 0.5.24-19981002)
> Driving: g77 -v -c -xf77-version /dev/null -xnone
> Reading specs from
/usr/lib/gcc-lib/i386-slackware-linux/egcs-2.91.66/specs
> gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)
>

/usr/lib/gcc-lib/i386-slackware-linux/egcs-2.91.66/cpp -lang-c -
v -undef -D__GNUC__=2 -D__GNUC_MINOR__=91 -D__ELF__ -D__unix__ -
D__i386__ -D__i386__ -D__linux__ -D__unix -D__i386 -D__linux -As
ystem(posix) -D_LANGUAGE_FORTRAN -traditional -Asystem(unix) -Ac
pu(i386) -Amachine(i386) -Di386 -D__i386 -D__i386__ /dev/null
/dev/null
> GNU CPP version egcs-2.91.66 19990314/Linux (egcs-1.1.2
release) (i386 Linux/ELF)
> #include "..." search starts here:
> #include <...> search starts here:
>  /usr/local/include
>  /usr/lib/gcc-lib/i386-slackware-linux/egcs-2.91.66/include
>  /usr/include
> End of search list.
>

/usr/lib/gcc-lib/i386-slackware-linux/egcs-2.91.66/f771 -fnull-v
ersion -quiet -dumpbase g77-version.f -version -fversion -o
/tmp/ccStiDag.s /dev/null
> GNU F77 version egcs-2.91.66 19990314/Linux (egcs-1.1.2
release) (i386-slackware-linux) compiled by GNU C version
egcs-2.91.66 19990314 (egcs-1.1.2 release).
> GNU Fortran Front End version 0.5.24-19981002
>  /usr/i386-slackware-linux/bin/as -V -Qy -o /tmp/ccgtlWDn.o
/tmp/ccStiDag.s
> GNU assembler version 2.9.1 (i386-slackware-linux), using BFD
version 2.9.1.0.25
>  /usr/i386-slackware-linux/bin/ld -m elf_i386 -dynamic-linker
/lib/ld-linux.so.2 -o /tmp/ccerWHQw /tmp/ccgtlWDn.o
/usr/lib/crt1.o /usr/lib/crti.o
/usr/lib/gcc-lib/i386-slackware-linux/egcs-2.91.66/crtbegin.o -L
/usr/lib/gcc-lib/i386-slackware-linux/egcs-2.91.66 -L/usr/i386-s
lackware-linux/lib -lg2c -lm -lgcc -lc -lgcc
/usr/lib/gcc-lib/i386-slackware-linux/egcs-2.91.66/crtend.o
/usr/lib/crtn.o
>  /tmp/ccerWHQw
> __G77_LIBF77_VERSION__: 0.5.24
> @(#)LIBF77 VERSION 19970919
> __G77_LIBI77_VERSION__: 0.5.24-19981021
> @(#) LIBI77 VERSION pjw,dmg-mods 19980617
> __G77_LIBU77_VERSION__: 0.5.24-19990305
> @(#) LIBU77 VERSION 19980709
>
> --------------------------------------------------------------
-------