Re: vrp bitfield miscompilation (WAS: [Regression] snd_emu10k1 doesn't work after GCC 4.2 upgrade)

On Monday 28 May 2007 08:22, Yuriy Tsibizov wrote:
> > -----Original Message-----
> > From: Yuriy Tsibizov
> > Sent: Sunday, May 27, 2007 1:42 AM
> > To: Yuriy Tsibizov; kabaev_at_gmail.com
> > Cc: current_at_freebsd.org
> > Subject: Re: [Regression] snd_emu10k1 doesn't work after GCC
> > 4.2 upgrade
> >
> > See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32100
>
> Use of following variables _can_ be affected by above miscompilation
> (these are signed single-bit variables):
>
> amd64/amd64/mp_machdep.c:	int	cpu_present:1;
> amd64/amd64/mp_machdep.c:	int	cpu_bsp:1;
> amd64/amd64/mp_machdep.c:	int	cpu_disabled:1;
> dev/acpica/acpi_pci_link.c:	int	l_routed:1;
> dev/acpica/acpi_pci_link.c:	int	l_isa_irq:1;
> dev/sound/isa/ess.c:    	int type, duplex:1, newspeed:1;
> dev/sound/pci/emu10k1.c:	int b16:1, stereo:1, busy:1, running:1,
> ismaster:1;
> dev/sound/pci/solo.c:    	int simplex_dir, type, duplex:1,
> newspeed:1, dmasz[2];
> dev/puc/puc.c:	int		p_hasintr:1;
> dev/puc/puc_bfe.h:	int		sc_fastintr:1;
> dev/puc/puc_bfe.h:	int		sc_leaving:1;
> dev/puc/puc_bfe.h:	int		sc_polled:1;
> dev/rp/rpvar.h:	int			rp_rts_iflow:1;
> dev/rp/rpvar.h:	int			rp_disable_writes:1;
> dev/rp/rpvar.h:	int			rp_cts:1;
> dev/rp/rpvar.h:	int			rp_waiting:1;
> dev/rp/rpvar.h:	int			rp_xmit_stopped:1;
> dev/scc/scc_bfe.h:	int		m_attached:1;
> dev/scc/scc_bfe.h:	int		m_fastintr:1;
> dev/scc/scc_bfe.h:	int		m_hasintr:1;
> dev/scc/scc_bfe.h:	int		m_probed:1;
> dev/scc/scc_bfe.h:	int		m_sysdev:1;
> dev/scc/scc_bfe.h:	int		ch_enabled:1;
> dev/scc/scc_bfe.h:	int		ch_sysdev:1;
> dev/scc/scc_bfe.h:	int		sc_fastintr:1;
> dev/scc/scc_bfe.h:	int		sc_leaving:1;
> dev/scc/scc_bfe.h:	int		sc_polled:1;
> dev/uart/uart_bus.h:	int		sc_callout:1;	/* This UART is
> opened for callout. */
> dev/uart/uart_bus.h:	int		sc_fastintr:1;	/* This UART
> uses fast interrupts. */
> dev/uart/uart_bus.h:	int		sc_hwiflow:1;	/* This UART has
> HW input flow ctl. */
> dev/uart/uart_bus.h:	int		sc_hwoflow:1;	/* This UART has
> HW output flow ctl. */
> dev/uart/uart_bus.h:	int		sc_leaving:1;	/* This UART is
> going away. */
> dev/uart/uart_bus.h:	int		sc_opened:1;	/* This UART is
> open for business. */
> dev/uart/uart_bus.h:	int		sc_polled:1;	/* This UART has
> no interrupts. */
> dev/uart/uart_bus.h:	int		sc_txbusy:1;	/* This UART is
> transmitting. */
> fs/pseudofs/pseudofs_internal.h:	int		 pvd_dead:1;
> geom/part/g_part.h:	int		gpe_created:1;	/* Entry is
> newly created. */
> geom/part/g_part.h:	int		gpe_deleted:1;	/* Entry has
> been deleted. */
> geom/part/g_part.h:	int		gpe_modified:1;	/* Entry has
> been modified. */
> geom/part/g_part.h:	int		gpt_isleaf:1;	/* Cannot be
> sub-partitioned. */
> geom/part/g_part.h:	int		gpt_created:1;	/* Newly
> created. */
> geom/part/g_part.h:	int		gpt_modified:1;	/* Table changes
> have been made. */
> geom/part/g_part.h:	int		gpt_opened:1;	/* Permissions
> obtained. */
> i386/i386/mp_machdep.c:	int	cpu_present:1;
> i386/i386/mp_machdep.c:	int	cpu_bsp:1;
> i386/i386/mp_machdep.c:	int	cpu_disabled:1;
> i386/include/npx.h:	int	fp_sgn:1;	/* mantissa sign */
> sparc64/pci/psycho.c:		int apb:1;
> sparc64/pci/psycho.c:		int ppb:1;
>
> I can't say that there _is_ a miscompilation related to all variables in
> this list.
>
> Should most of them (I'm not shure for fp_sign) be changed to unsigned
> int? With (signed) int these flags have values of (-1;0), with unsigned
> int they will use more obvious (0;1) values.
>
>
> Yuriy.

Interesting find. Another issue:

I've seen that the compile will round the memory size of a bit-fields down to 
the nearest byte, if you turn on optimization. I think you should 
use "uint8_t".

--HPS