Package: ghdl
Version: 0.29+gcc4.3.4+dfsg-1
Severity: serious
--- Please enter the report below this line. ---
Hi
I noticed that ghdl check for uninitialized generics that are defined
in the top level only.
In this example there is an uninitialized generic which is defined in
the top level :
jo...@pc:~/a$ ghdl -a good.vhd
jo...@pc:~/a$ ghdl -e tb
error: entity "tb" cannot be at the top of a design
good.vhd:16:13: (generic "n_bits_data" has no default value)
/usr/lib/ghdl/bin/ghdl: compilation error
jo...@pc:~/a$
Then ghdl rightly complains during the elaboration.
But when there is a generic that isn't defined in the top level, ghdl
won't check if it is initialized or not.
See the following example :
jo...@pc:~/a$ ghdl -a bad.vhd
jo...@pc:~/a$ ghdl -e tb
Here ghdl should complain that there is an uninitialized generic, but
it doesn't because the generic is not defined in the top level.
jo...@pc:~/a$ ghdl -r tb
Now ghdl is trying to eat a huge amount of memory and I quickly have to
kill it before the whole system hangs !!!!
There is more explanations in the examples (put in attachement)
Bye
Jonas
--- System information. ---
Architecture: i386
Kernel: Linux 2.6.32-3-686
Debian Release: squeeze/sid
500 testing ftp.de.debian.org
111 unstable ftp.de.debian.org
110 experimental ftp.de.debian.org
--- Package information. ---
Depends (Version) | Installed
=============================-+-=============
libc6 (>= 2.7) | 2.10.2-6
libgcc1 (>= 1:4.1.1) | 1:4.4.2-9
libgmp3c2 | 2:4.3.2+dfsg-1
libgnat-4.4 (>= 4.4.3-1) | 4.4.3-1
libmpfr1ldbl | 2.4.2-3
gnat-4.4 | 4.4.3-1
zlib1g-dev | 1:1.2.3.4.dfsg-3
Recommends (Version) | Installed
=========================-+-===========
gtkwave | 3.3.3-1
Package's Suggests field is empty.
--
<[email protected]>
library ieee;
use ieee.std_logic_1164.all;
-- COMPONENT
entity a is
generic (N_BITS_DATA : integer);
end entity;
architecture arch_a of a is
begin
end;
--
-- TESTBENCH
entity tb is
generic (N_BITS_DATA : integer);
end;
architecture arch_tb of tb is
begin
end;
--
library ieee;
use ieee.std_logic_1164.all;
-- COMPONENT
entity a is
-- N_BITS_DATA is nowhere initialized. This problem should be catched during
-- elaboration but it isn't !
-- During simulation I found that the value of N_BITS_DATA is -2147483648 and
-- that the value of N_BITS_DATA-1 is 2147483647 !!!!
generic (N_BITS_DATA : integer);
end entity;
architecture arch_a of a is
--~ -- Here data_s will have 4_194_305 elements and this will make ghdl
--~ -- take about 650 MB of memory. According to that, each element take about 150 B
--~ signal data_s : std_logic_vector((N_BITS_DATA-1)/512 downto 0);
-- This line make ghdl eat all the free memory because it is trying to make a
-- vector of 2**31 elements !!!! And there isn't enough memory because we need
-- about 2**31 * 150 B = ~ 300 GB !!!!
signal data_s : std_logic_vector(N_BITS_DATA-1 downto 0);
--~ -- Strangely this line doesn't make the simulation failed because N_BITS_DATA
--~ -- is negativ, but it doesn't increase the use of memory either.
--~ signal data_s : std_logic_vector(N_BITS_DATA downto 0);
begin
process begin
-- N_BITS_DATA = -2147483648 = -2**31
report integer'image(N_BITS_DATA);
--
-- N_BITS_DATA-1 = 2147483647 = 2**31 - 1
report integer'image(N_BITS_DATA-1);
--
-- (N_BITS_DATA-1)/512 = 4_194_304 = 2**22
report integer'image((N_BITS_DATA-1)/512);
--
end process;
end;
--
-- TESTBENCH
entity tb is end entity;
architecture arch_tb of tb is
begin
X1: entity work.a;
end;
--
