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authorMichal Nazarewicz <mina86@mina86.com>2016-01-16 01:57:58 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-16 20:17:22 +0100
commit8f57e4d930d48217268315898212518d4d3e0773 (patch)
tree7a21dc58268fd6dfd9d1399e3765fa0c99aa561e /drivers/iio
parentinclude/linux/poison.h: use POISON_POINTER_DELTA for poison pointers (diff)
downloadlinux-8f57e4d930d48217268315898212518d4d3e0773.tar.xz
linux-8f57e4d930d48217268315898212518d4d3e0773.zip
include/linux/kernel.h: change abs() macro so it uses consistent return type
Rewrite abs() so that its return type does not depend on the architecture and no unexpected type conversion happen inside of it. The only conversion is from unsigned to signed type. char is left as a return type but treated as a signed type regradless of it's actual signedness. With the old version, int arguments were promoted to long and depending on architecture a long argument might result in s64 or long return type (which may or may not be the same). This came after some back and forth with Nicolas. The current macro has different return type (for the same input type) depending on architecture which might be midly iritating. An alternative version would promote to int like so: #define abs(x) __abs_choose_expr(x, long long, \ __abs_choose_expr(x, long, \ __builtin_choose_expr( \ sizeof(x) <= sizeof(int), \ ({ int __x = (x); __x<0?-__x:__x; }), \ ((void)0)))) I have no preference but imagine Linus might. :] Nicolas argument against is that promoting to int causes iconsistent behaviour: int main(void) { unsigned short a = 0, b = 1, c = a - b; unsigned short d = abs(a - b); unsigned short e = abs(c); printf("%u %u\n", d, e); // prints: 1 65535 } Then again, no sane person expects consistent behaviour from C integer arithmetic. ;) Note: __builtin_types_compatible_p(unsigned char, char) is always false, and __builtin_types_compatible_p(signed char, char) is also always false. Signed-off-by: Michal Nazarewicz <mina86@mina86.com> Reviewed-by: Nicolas Pitre <nico@linaro.org> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: Wey-Yi Guy <wey-yi.w.guy@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/iio')
-rw-r--r--drivers/iio/industrialio-core.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index fd01f3493fc7..af7cc1e65656 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -433,16 +433,15 @@ ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
scale_db = true;
case IIO_VAL_INT_PLUS_MICRO:
if (vals[1] < 0)
- return sprintf(buf, "-%ld.%06u%s\n", abs(vals[0]),
- -vals[1],
- scale_db ? " dB" : "");
+ return sprintf(buf, "-%d.%06u%s\n", abs(vals[0]),
+ -vals[1], scale_db ? " dB" : "");
else
return sprintf(buf, "%d.%06u%s\n", vals[0], vals[1],
scale_db ? " dB" : "");
case IIO_VAL_INT_PLUS_NANO:
if (vals[1] < 0)
- return sprintf(buf, "-%ld.%09u\n", abs(vals[0]),
- -vals[1]);
+ return sprintf(buf, "-%d.%09u\n", abs(vals[0]),
+ -vals[1]);
else
return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
case IIO_VAL_FRACTIONAL: