vrp bitfield miscompilation (WAS: [Regression] snd_emu10k1
doesn't work after GCC 4.2 upgrade)
Hans Petter Selasky
hselasky at c2i.net
Mon May 28 07:57:25 UTC 2007
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
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