https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111675
Bug ID: 111675
Summary: Incorrect parameter value passed when attempting to
pass a field of a packed record as a parameter
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: modula2
Assignee: gaius at gcc dot gnu.org
Reporter: gaius at gcc dot gnu.org
Target Milestone: ---
Summary cannot pass a packed field by value to a procedure as it results in a
garbled value.
Consider the example below, if compiled and run we get:
$ gm2 -g packedrecord3.mod
$ ./a.out
failed to pass 0 into test
$ gdb ./a.out
(gdb) break printf
(gdb) run
Breakpoint 3, __printf (format=0x402008 "failed to pass %d into test\n")
(gdb) where
#0 __printf (format=0x402008 "failed to pass %d into test\n") at printf.c:28
#1 0x0000000000401387 in test (s=36893488147419103232, level=0) at
packedrecord3.mod:25
#2 0x00000000004012ce in _M2_packedrecord3_init (argc=1, argv=0x7fffffffe448,
envp=0x7fffffffe458) at packedrecord3.mod:47
oddly print sizeof s gives 16 !
module packedrecord3 ; (*!m2iso+gm2*)
from libc import printf, exit ;
type
subrange = [0..63] ;
packedrec = record
<* bytealignment (0) *>
bool: boolean ;
col : (white, black) ;
sub : subrange ;
end ;
var
global: subrange ;
pr : packedrec ;
procedure test (s: subrange; level: cardinal) ;
begin
if s # global
then
printf ("failed to pass %d into test\n", ord (s)) ;
exit (1)
end ;
if level > 0
then
test (s, level-1)
end
end test ;
begin
if size (pr) # 1
then
printf ("test failed as size (pr) should be 1 not %d\n", size (pr)) ;
exit (1)
end ;
for global := min (subrange) to max (subrange) do
test (global, 2)
end ;
for global := min (subrange) to max (subrange) do
pr.bool := false ;
pr.sub := global ;
test (pr.sub, 2)
end
end packedrecord3.
