hw/usb/hcd-xhci.h | 2 +- include/block/block.h | 4 +-- include/exec/cpu-all.h | 8 +++--- include/exec/cpu-defs.h | 7 +++++- include/qemu/osdep.h | 51 +++++++++++++++++++++++++++++++++------ accel/tcg/translate-all.c | 6 ++--- migration/qemu-file.c | 2 +- 7 files changed, 59 insertions(+), 21 deletions(-)
I'm not aware of any immediate bugs in qemu where a second runtime
evalution of the arguments to MIN() or MAX() causes a problem, but
proactively preventing such abuse is easier than falling prey to an
unintended case down the road. At any rate, here's the conversation
that sparked the current patch:
https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg05718.html
Update the MIN/MAX macros to only evaluate their argument once at
runtime; this uses typeof(1 ? (a) : (b)) to ensure that we are
promoting the temporaries to the same type as the final comparison (we
have to trigger type promotion, as typeof(bitfield) won't compile; and
we can't use typeof((a) + (b)) or even typeof((a) + 0), as some of our
uses of MAX are on void* pointers where such addition is undefined).
However, we are unable to work around gcc refusing to compile ({}) in
a constant context (such as the array length of a static variable),
even when only used in the dead branch of a __builtin_choose_expr(),
so we have to provide a second macro pair MIN_CONST and MAX_CONST for
use when both arguments are known to be compile-time constants and
where the result must also be usable as a constant; this second form
evaluates arguments multiple times but that doesn't matter for
constants. By using a void expression as the expansion if a
non-constant is presented to this second form, we can enlist the
compiler to ensure the double evaluation is not attempted on
non-constants.
Alas, as both macros now rely on compiler intrinsics, they are no
longer usable in preprocessor #if conditions; those will just have to
be open-coded or the logic rewritten into #define or runtime 'if'
conditions (but where the compiler dead-code-elimination will probably
still apply).
I tested that both gcc 10.1.1 and clang 10.0.0 produce errors for all
forms of macro mis-use. As the errors can sometimes be cryptic, I'm
demonstrating the gcc output:
Use of MIN when MIN_CONST is needed:
In file included from /home/eblake/qemu/qemu-img.c:25:
/home/eblake/qemu/include/qemu/osdep.h:249:5: error: braced-group within expression allowed only inside a function
249 | ({ \
| ^
/home/eblake/qemu/qemu-img.c:92:12: note: in expansion of macro ‘MIN’
92 | char array[MIN(1, 2)] = "";
| ^~~
Use of MIN_CONST when MIN is needed:
/home/eblake/qemu/qemu-img.c: In function ‘is_allocated_sectors’:
/home/eblake/qemu/qemu-img.c:1225:15: error: void value not ignored as it ought to be
1225 | i = MIN_CONST(i, n);
| ^
Use of MIN in the preprocessor:
In file included from /home/eblake/qemu/accel/tcg/translate-all.c:20:
/home/eblake/qemu/accel/tcg/translate-all.c: In function ‘page_check_range’:
/home/eblake/qemu/include/qemu/osdep.h:249:6: error: token "{" is not valid in preprocessor expressions
249 | ({ \
| ^
Fix the resulting callsites that used #if or computed a compile-time
constant min or max to use the new macros. cpu-defs.h is interesting,
as CPU_TLB_DYN_MAX_BITS is sometimes used as a constant and sometimes
dynamic.
Signed-off-by: Eric Blake <eblake@redhat.com>
---
v2 was: https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg00727.html
v3: avoid __auto_type [Richard], document other approaches that fail
[Dave], rebase to master
v4: use ((void)0) instead of __builtin_unreachable [Dave], update comments
---
hw/usb/hcd-xhci.h | 2 +-
include/block/block.h | 4 +--
include/exec/cpu-all.h | 8 +++---
include/exec/cpu-defs.h | 7 +++++-
include/qemu/osdep.h | 51 +++++++++++++++++++++++++++++++++------
accel/tcg/translate-all.c | 6 ++---
migration/qemu-file.c | 2 +-
7 files changed, 59 insertions(+), 21 deletions(-)
diff --git a/hw/usb/hcd-xhci.h b/hw/usb/hcd-xhci.h
index 2fad4df2a704..946af51fc25d 100644
--- a/hw/usb/hcd-xhci.h
+++ b/hw/usb/hcd-xhci.h
@@ -214,7 +214,7 @@ struct XHCIState {
uint32_t dcbaap_high;
uint32_t config;
- USBPort uports[MAX(MAXPORTS_2, MAXPORTS_3)];
+ USBPort uports[MAX_CONST(MAXPORTS_2, MAXPORTS_3)];
XHCIPort ports[MAXPORTS];
XHCISlot slots[MAXSLOTS];
uint32_t numports;
diff --git a/include/block/block.h b/include/block/block.h
index 25e299605e19..e8fc8149967f 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -133,8 +133,8 @@ typedef struct HDGeometry {
#define BDRV_SECTOR_BITS 9
#define BDRV_SECTOR_SIZE (1ULL << BDRV_SECTOR_BITS)
-#define BDRV_REQUEST_MAX_SECTORS MIN(SIZE_MAX >> BDRV_SECTOR_BITS, \
- INT_MAX >> BDRV_SECTOR_BITS)
+#define BDRV_REQUEST_MAX_SECTORS MIN_CONST(SIZE_MAX >> BDRV_SECTOR_BITS, \
+ INT_MAX >> BDRV_SECTOR_BITS)
#define BDRV_REQUEST_MAX_BYTES (BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS)
/*
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index d14374bdd499..291454fac12e 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -176,11 +176,9 @@ extern unsigned long reserved_va;
* avoid setting bits at the top of guest addresses that might need
* to be used for tags.
*/
-#if MIN(TARGET_VIRT_ADDR_SPACE_BITS, TARGET_ABI_BITS) <= 32
-# define GUEST_ADDR_MAX_ UINT32_MAX
-#else
-# define GUEST_ADDR_MAX_ (~0ul)
-#endif
+#define GUEST_ADDR_MAX_ \
+ ((MIN_CONST(TARGET_VIRT_ADDR_SPACE_BITS, TARGET_ABI_BITS) <= 32) ? \
+ UINT32_MAX : ~0ul)
#define GUEST_ADDR_MAX (reserved_va ? reserved_va - 1 : GUEST_ADDR_MAX_)
#else
diff --git a/include/exec/cpu-defs.h b/include/exec/cpu-defs.h
index 8c44abefa22a..918563233797 100644
--- a/include/exec/cpu-defs.h
+++ b/include/exec/cpu-defs.h
@@ -102,8 +102,13 @@ typedef uint64_t target_ulong;
* Skylake's Level-2 STLB has 16 1G entries.
* Also, make sure we do not size the TLB past the guest's address space.
*/
-# define CPU_TLB_DYN_MAX_BITS \
+# ifdef TARGET_PAGE_BITS_VARY
+# define CPU_TLB_DYN_MAX_BITS \
MIN(22, TARGET_VIRT_ADDR_SPACE_BITS - TARGET_PAGE_BITS)
+# else
+# define CPU_TLB_DYN_MAX_BITS \
+ MIN_CONST(22, TARGET_VIRT_ADDR_SPACE_BITS - TARGET_PAGE_BITS)
+# endif
# endif
typedef struct CPUTLBEntry {
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index ff7c17b85735..b18584f32ff6 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -236,18 +236,53 @@ extern int daemon(int, int);
#define SIZE_MAX ((size_t)-1)
#endif
-#ifndef MIN
-#define MIN(a, b) (((a) < (b)) ? (a) : (b))
-#endif
-#ifndef MAX
-#define MAX(a, b) (((a) > (b)) ? (a) : (b))
-#endif
+/*
+ * Two variations of MIN/MAX macros. The first is for runtime use, and
+ * evaluates arguments only once (so it is safe even with side
+ * effects), but will not work in constant contexts (such as array
+ * size declarations) because of the '{}'. The second is for constant
+ * expression use, where evaluating arguments twice is safe because
+ * the result is going to be constant anyway, but will not work in a
+ * runtime context because of a void expression where a value is
+ * expected. Thus, both gcc and clang will fail to compile if you use
+ * the wrong macro (even if the error may seem a bit cryptic).
+ *
+ * Note that neither form is usable as an #if condition; if you truly
+ * need to write conditional code that depends on a minimum or maximum
+ * determined by the pre-processor instead of the compiler, you'll
+ * have to open-code it.
+ */
+#undef MIN
+#define MIN(a, b) \
+ ({ \
+ typeof(1 ? (a) : (b)) _a = (a), _b = (b); \
+ _a < _b ? _a : _b; \
+ })
+#define MIN_CONST(a, b) \
+ __builtin_choose_expr( \
+ __builtin_constant_p(a) && __builtin_constant_p(b), \
+ (a) < (b) ? (a) : (b), \
+ ((void)0))
+#undef MAX
+#define MAX(a, b) \
+ ({ \
+ typeof(1 ? (a) : (b)) _a = (a), _b = (b); \
+ _a > _b ? _a : _b; \
+ })
+#define MAX_CONST(a, b) \
+ __builtin_choose_expr( \
+ __builtin_constant_p(a) && __builtin_constant_p(b), \
+ (a) > (b) ? (a) : (b), \
+ __builtin_unreachable())
/* Minimum function that returns zero only iff both values are zero.
* Intended for use with unsigned values only. */
#ifndef MIN_NON_ZERO
-#define MIN_NON_ZERO(a, b) ((a) == 0 ? (b) : \
- ((b) == 0 ? (a) : (MIN(a, b))))
+#define MIN_NON_ZERO(a, b) \
+ ({ \
+ typeof(1 ? (a) : (b)) _a = (a), _b = (b); \
+ _a == 0 ? _b : (_b == 0 || _b > _a) ? _a : _b; \
+ })
#endif
/* Round number down to multiple */
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 42ce1dfcff77..d77add79b218 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -2565,9 +2565,9 @@ int page_check_range(target_ulong start, target_ulong len, int flags)
/* This function should never be called with addresses outside the
guest address space. If this assert fires, it probably indicates
a missing call to h2g_valid. */
-#if TARGET_ABI_BITS > L1_MAP_ADDR_SPACE_BITS
- assert(start < ((target_ulong)1 << L1_MAP_ADDR_SPACE_BITS));
-#endif
+ if (TARGET_ABI_BITS > L1_MAP_ADDR_SPACE_BITS) {
+ assert(start < ((target_ulong)1 << L1_MAP_ADDR_SPACE_BITS));
+ }
if (len == 0) {
return 0;
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 1c3a358a140d..be21518c5708 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -31,7 +31,7 @@
#include "qapi/error.h"
#define IO_BUF_SIZE 32768
-#define MAX_IOV_SIZE MIN(IOV_MAX, 64)
+#define MAX_IOV_SIZE MIN_CONST(IOV_MAX, 64)
struct QEMUFile {
const QEMUFileOps *ops;
--
2.27.0
On 6/4/20 4:52 PM, Eric Blake wrote: > I'm not aware of any immediate bugs in qemu where a second runtime > evalution of the arguments to MIN() or MAX() causes a problem, but evaluation > proactively preventing such abuse is easier than falling prey to an > unintended case down the road. At any rate, here's the conversation > that sparked the current patch: > https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg05718.html > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
On 6/4/20 2:52 PM, Eric Blake wrote: > I'm not aware of any immediate bugs in qemu where a second runtime > evalution of the arguments to MIN() or MAX() causes a problem, but > proactively preventing such abuse is easier than falling prey to an > unintended case down the road. At any rate, here's the conversation > that sparked the current patch: > https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg05718.html > > Update the MIN/MAX macros to only evaluate their argument once at > runtime; this uses typeof(1 ? (a) : (b)) to ensure that we are > promoting the temporaries to the same type as the final comparison (we > have to trigger type promotion, as typeof(bitfield) won't compile; and > we can't use typeof((a) + (b)) or even typeof((a) + 0), as some of our > uses of MAX are on void* pointers where such addition is undefined). > > However, we are unable to work around gcc refusing to compile ({}) in > a constant context (such as the array length of a static variable), > even when only used in the dead branch of a __builtin_choose_expr(), > so we have to provide a second macro pair MIN_CONST and MAX_CONST for > use when both arguments are known to be compile-time constants and > where the result must also be usable as a constant; this second form > evaluates arguments multiple times but that doesn't matter for > constants. By using a void expression as the expansion if a > non-constant is presented to this second form, we can enlist the > compiler to ensure the double evaluation is not attempted on > non-constants. > > Alas, as both macros now rely on compiler intrinsics, they are no > longer usable in preprocessor #if conditions; those will just have to > be open-coded or the logic rewritten into #define or runtime 'if' > conditions (but where the compiler dead-code-elimination will probably > still apply). > > I tested that both gcc 10.1.1 and clang 10.0.0 produce errors for all > forms of macro mis-use. As the errors can sometimes be cryptic, I'm > demonstrating the gcc output: > > Use of MIN when MIN_CONST is needed: > > In file included from /home/eblake/qemu/qemu-img.c:25: > /home/eblake/qemu/include/qemu/osdep.h:249:5: error: braced-group within expression allowed only inside a function > 249 | ({ \ > | ^ > /home/eblake/qemu/qemu-img.c:92:12: note: in expansion of macro ‘MIN’ > 92 | char array[MIN(1, 2)] = ""; > | ^~~ > > Use of MIN_CONST when MIN is needed: > > /home/eblake/qemu/qemu-img.c: In function ‘is_allocated_sectors’: > /home/eblake/qemu/qemu-img.c:1225:15: error: void value not ignored as it ought to be > 1225 | i = MIN_CONST(i, n); > | ^ > > Use of MIN in the preprocessor: > > In file included from /home/eblake/qemu/accel/tcg/translate-all.c:20: > /home/eblake/qemu/accel/tcg/translate-all.c: In function ‘page_check_range’: > /home/eblake/qemu/include/qemu/osdep.h:249:6: error: token "{" is not valid in preprocessor expressions > 249 | ({ \ > | ^ > > Fix the resulting callsites that used #if or computed a compile-time > constant min or max to use the new macros. cpu-defs.h is interesting, > as CPU_TLB_DYN_MAX_BITS is sometimes used as a constant and sometimes > dynamic. > > Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
On 04/06/20 23:52, Eric Blake wrote: > I'm not aware of any immediate bugs in qemu where a second runtime > evalution of the arguments to MIN() or MAX() causes a problem, but > proactively preventing such abuse is easier than falling prey to an > unintended case down the road. At any rate, here's the conversation > that sparked the current patch: > https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg05718.html > > Update the MIN/MAX macros to only evaluate their argument once at > runtime; this uses typeof(1 ? (a) : (b)) to ensure that we are > promoting the temporaries to the same type as the final comparison (we > have to trigger type promotion, as typeof(bitfield) won't compile; and > we can't use typeof((a) + (b)) or even typeof((a) + 0), as some of our > uses of MAX are on void* pointers where such addition is undefined). > > However, we are unable to work around gcc refusing to compile ({}) in > a constant context (such as the array length of a static variable), > even when only used in the dead branch of a __builtin_choose_expr(), > so we have to provide a second macro pair MIN_CONST and MAX_CONST for > use when both arguments are known to be compile-time constants and > where the result must also be usable as a constant; this second form > evaluates arguments multiple times but that doesn't matter for > constants. By using a void expression as the expansion if a > non-constant is presented to this second form, we can enlist the > compiler to ensure the double evaluation is not attempted on > non-constants. > > Alas, as both macros now rely on compiler intrinsics, they are no > longer usable in preprocessor #if conditions; those will just have to > be open-coded or the logic rewritten into #define or runtime 'if' > conditions (but where the compiler dead-code-elimination will probably > still apply). > > I tested that both gcc 10.1.1 and clang 10.0.0 produce errors for all > forms of macro mis-use. As the errors can sometimes be cryptic, I'm > demonstrating the gcc output: > > Use of MIN when MIN_CONST is needed: > > In file included from /home/eblake/qemu/qemu-img.c:25: > /home/eblake/qemu/include/qemu/osdep.h:249:5: error: braced-group within expression allowed only inside a function > 249 | ({ \ > | ^ > /home/eblake/qemu/qemu-img.c:92:12: note: in expansion of macro ‘MIN’ > 92 | char array[MIN(1, 2)] = ""; > | ^~~ > > Use of MIN_CONST when MIN is needed: > > /home/eblake/qemu/qemu-img.c: In function ‘is_allocated_sectors’: > /home/eblake/qemu/qemu-img.c:1225:15: error: void value not ignored as it ought to be > 1225 | i = MIN_CONST(i, n); > | ^ > > Use of MIN in the preprocessor: > > In file included from /home/eblake/qemu/accel/tcg/translate-all.c:20: > /home/eblake/qemu/accel/tcg/translate-all.c: In function ‘page_check_range’: > /home/eblake/qemu/include/qemu/osdep.h:249:6: error: token "{" is not valid in preprocessor expressions > 249 | ({ \ > | ^ > > Fix the resulting callsites that used #if or computed a compile-time > constant min or max to use the new macros. cpu-defs.h is interesting, > as CPU_TLB_DYN_MAX_BITS is sometimes used as a constant and sometimes > dynamic. > > Signed-off-by: Eric Blake <eblake@redhat.com> > > --- > > v2 was: https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg00727.html > v3: avoid __auto_type [Richard], document other approaches that fail > [Dave], rebase to master > v4: use ((void)0) instead of __builtin_unreachable [Dave], update comments > --- > hw/usb/hcd-xhci.h | 2 +- > include/block/block.h | 4 +-- > include/exec/cpu-all.h | 8 +++--- > include/exec/cpu-defs.h | 7 +++++- > include/qemu/osdep.h | 51 +++++++++++++++++++++++++++++++++------ > accel/tcg/translate-all.c | 6 ++--- > migration/qemu-file.c | 2 +- > 7 files changed, 59 insertions(+), 21 deletions(-) > > diff --git a/hw/usb/hcd-xhci.h b/hw/usb/hcd-xhci.h > index 2fad4df2a704..946af51fc25d 100644 > --- a/hw/usb/hcd-xhci.h > +++ b/hw/usb/hcd-xhci.h > @@ -214,7 +214,7 @@ struct XHCIState { > uint32_t dcbaap_high; > uint32_t config; > > - USBPort uports[MAX(MAXPORTS_2, MAXPORTS_3)]; > + USBPort uports[MAX_CONST(MAXPORTS_2, MAXPORTS_3)]; > XHCIPort ports[MAXPORTS]; > XHCISlot slots[MAXSLOTS]; > uint32_t numports; > diff --git a/include/block/block.h b/include/block/block.h > index 25e299605e19..e8fc8149967f 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -133,8 +133,8 @@ typedef struct HDGeometry { > #define BDRV_SECTOR_BITS 9 > #define BDRV_SECTOR_SIZE (1ULL << BDRV_SECTOR_BITS) > > -#define BDRV_REQUEST_MAX_SECTORS MIN(SIZE_MAX >> BDRV_SECTOR_BITS, \ > - INT_MAX >> BDRV_SECTOR_BITS) > +#define BDRV_REQUEST_MAX_SECTORS MIN_CONST(SIZE_MAX >> BDRV_SECTOR_BITS, \ > + INT_MAX >> BDRV_SECTOR_BITS) > #define BDRV_REQUEST_MAX_BYTES (BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS) > > /* > diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h > index d14374bdd499..291454fac12e 100644 > --- a/include/exec/cpu-all.h > +++ b/include/exec/cpu-all.h > @@ -176,11 +176,9 @@ extern unsigned long reserved_va; > * avoid setting bits at the top of guest addresses that might need > * to be used for tags. > */ > -#if MIN(TARGET_VIRT_ADDR_SPACE_BITS, TARGET_ABI_BITS) <= 32 > -# define GUEST_ADDR_MAX_ UINT32_MAX > -#else > -# define GUEST_ADDR_MAX_ (~0ul) > -#endif > +#define GUEST_ADDR_MAX_ \ > + ((MIN_CONST(TARGET_VIRT_ADDR_SPACE_BITS, TARGET_ABI_BITS) <= 32) ? \ > + UINT32_MAX : ~0ul) > #define GUEST_ADDR_MAX (reserved_va ? reserved_va - 1 : GUEST_ADDR_MAX_) > > #else > diff --git a/include/exec/cpu-defs.h b/include/exec/cpu-defs.h > index 8c44abefa22a..918563233797 100644 > --- a/include/exec/cpu-defs.h > +++ b/include/exec/cpu-defs.h > @@ -102,8 +102,13 @@ typedef uint64_t target_ulong; > * Skylake's Level-2 STLB has 16 1G entries. > * Also, make sure we do not size the TLB past the guest's address space. > */ > -# define CPU_TLB_DYN_MAX_BITS \ > +# ifdef TARGET_PAGE_BITS_VARY > +# define CPU_TLB_DYN_MAX_BITS \ > MIN(22, TARGET_VIRT_ADDR_SPACE_BITS - TARGET_PAGE_BITS) > +# else > +# define CPU_TLB_DYN_MAX_BITS \ > + MIN_CONST(22, TARGET_VIRT_ADDR_SPACE_BITS - TARGET_PAGE_BITS) > +# endif > # endif > > typedef struct CPUTLBEntry { > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > index ff7c17b85735..b18584f32ff6 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -236,18 +236,53 @@ extern int daemon(int, int); > #define SIZE_MAX ((size_t)-1) > #endif > > -#ifndef MIN > -#define MIN(a, b) (((a) < (b)) ? (a) : (b)) > -#endif > -#ifndef MAX > -#define MAX(a, b) (((a) > (b)) ? (a) : (b)) > -#endif > +/* > + * Two variations of MIN/MAX macros. The first is for runtime use, and > + * evaluates arguments only once (so it is safe even with side > + * effects), but will not work in constant contexts (such as array > + * size declarations) because of the '{}'. The second is for constant > + * expression use, where evaluating arguments twice is safe because > + * the result is going to be constant anyway, but will not work in a > + * runtime context because of a void expression where a value is > + * expected. Thus, both gcc and clang will fail to compile if you use > + * the wrong macro (even if the error may seem a bit cryptic). > + * > + * Note that neither form is usable as an #if condition; if you truly > + * need to write conditional code that depends on a minimum or maximum > + * determined by the pre-processor instead of the compiler, you'll > + * have to open-code it. > + */ > +#undef MIN > +#define MIN(a, b) \ > + ({ \ > + typeof(1 ? (a) : (b)) _a = (a), _b = (b); \ > + _a < _b ? _a : _b; \ > + }) > +#define MIN_CONST(a, b) \ > + __builtin_choose_expr( \ > + __builtin_constant_p(a) && __builtin_constant_p(b), \ > + (a) < (b) ? (a) : (b), \ > + ((void)0)) > +#undef MAX > +#define MAX(a, b) \ > + ({ \ > + typeof(1 ? (a) : (b)) _a = (a), _b = (b); \ > + _a > _b ? _a : _b; \ > + }) > +#define MAX_CONST(a, b) \ > + __builtin_choose_expr( \ > + __builtin_constant_p(a) && __builtin_constant_p(b), \ > + (a) > (b) ? (a) : (b), \ > + __builtin_unreachable()) > > /* Minimum function that returns zero only iff both values are zero. > * Intended for use with unsigned values only. */ > #ifndef MIN_NON_ZERO > -#define MIN_NON_ZERO(a, b) ((a) == 0 ? (b) : \ > - ((b) == 0 ? (a) : (MIN(a, b)))) > +#define MIN_NON_ZERO(a, b) \ > + ({ \ > + typeof(1 ? (a) : (b)) _a = (a), _b = (b); \ > + _a == 0 ? _b : (_b == 0 || _b > _a) ? _a : _b; \ > + }) > #endif > > /* Round number down to multiple */ > diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c > index 42ce1dfcff77..d77add79b218 100644 > --- a/accel/tcg/translate-all.c > +++ b/accel/tcg/translate-all.c > @@ -2565,9 +2565,9 @@ int page_check_range(target_ulong start, target_ulong len, int flags) > /* This function should never be called with addresses outside the > guest address space. If this assert fires, it probably indicates > a missing call to h2g_valid. */ > -#if TARGET_ABI_BITS > L1_MAP_ADDR_SPACE_BITS > - assert(start < ((target_ulong)1 << L1_MAP_ADDR_SPACE_BITS)); > -#endif > + if (TARGET_ABI_BITS > L1_MAP_ADDR_SPACE_BITS) { > + assert(start < ((target_ulong)1 << L1_MAP_ADDR_SPACE_BITS)); > + } > > if (len == 0) { > return 0; > diff --git a/migration/qemu-file.c b/migration/qemu-file.c > index 1c3a358a140d..be21518c5708 100644 > --- a/migration/qemu-file.c > +++ b/migration/qemu-file.c > @@ -31,7 +31,7 @@ > #include "qapi/error.h" > > #define IO_BUF_SIZE 32768 > -#define MAX_IOV_SIZE MIN(IOV_MAX, 64) > +#define MAX_IOV_SIZE MIN_CONST(IOV_MAX, 64) > > struct QEMUFile { > const QEMUFileOps *ops; > Queued, thnaks. Paolo
On Thursday, 2020-06-04 at 16:52:36 -05, Eric Blake wrote: > /* Minimum function that returns zero only iff both values are zero. Not your change, but "only" is unnecessary here (or iff -> if). dme. -- But uh oh, I love her because, she moves in her own way.
On 6/5/20 10:24 AM, David Edmondson wrote: > On Thursday, 2020-06-04 at 16:52:36 -05, Eric Blake wrote: > >> /* Minimum function that returns zero only iff both values are zero. > > Not your change, but "only" is unnecessary here (or iff -> if). Maybe we should teach checkpatch.pl to refuse the idiomatic 'iff', it is already hard enough for non-native English to read (or write) technical documentation...
On 6/5/20 3:24 AM, David Edmondson wrote: > On Thursday, 2020-06-04 at 16:52:36 -05, Eric Blake wrote: > >> /* Minimum function that returns zero only iff both values are zero. > > Not your change, but "only" is unnecessary here (or iff -> if). Indeed. Whoever picks this up could make that change (although I have no idea which tree will be best for this patch, so I may just adopt it as a miscellaneous patch through one of my own if there are no objections after a few days...). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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