Commit Graph

6 Commits

Author SHA1 Message Date
Nicolas Pitre
cf6fb4dea2 lib: cbprintf: float conversion optimization and documentation
While documenting the float conversion code, I found there was room
for some optimization. In doing so I added test cases to cover edge
cases e.g. making sure proper rounding is applied and that no loss
of precision was introduced. Compiled code should be smaller and
faster.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
2020-12-08 14:09:15 -05:00
Peter Bigot
c1b0cf8ec6 lib: cbprintf: work around LLVM code generation bug
LLVM building for qemu_x86 appears to have an optimization bug where a
union that is assigned to hold values read from va_args() is inferred
to be a constant value, so is placed in ROM with an all-zero content.

Prevent this by packing the conversion state and the value union into
a single container structure that's stack allocated.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
2020-11-19 12:37:33 +01:00
Peter Bigot
a9e2b10a86 lib: cbprintf: ignore l length modifier on float values
%lf is specified to be the same as %f, and should not be marked as
 invalid.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
2020-11-17 17:49:22 -05:00
Peter Bigot
607b390ba4 lib: cbprintf: fix pointer justification and padding
Although flags with pointers are not defined behavior, there is a
desire to have them work, so add a test and fix the complete
implementation so it passes.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
2020-11-17 11:34:25 +01:00
Martin Åberg
9feb799762 lib: cbprintf: improved %p specifier handling
This fixes an issue where the %p specifier always generated "(nil)"
on SPARC. The failing test cases were:
 tests/lib/sprintf/libraries.libc.sprintf
 tests/kernel/common/kernel.common.misra
 tests/kernel/common/kernel.common.tls
 tests/kernel/common/kernel.common

The exact logic behind the issue has not been fully analyzed, but
it can be observed that this commit eliminates one occurrence of
undefined behavior. (Only allowed to read the last union field written.)

Signed-off-by: Martin Åberg <martin.aberg@gaisler.com>
2020-11-13 14:53:55 -08:00
Peter Bigot
33103828dc lib: add cbprintf capability
This commit adds a C99 stdio value formatter capability where
generated text is emitted through a callback.  This allows generation
of arbitrarily long output without a buffer, functionality that is
core to printk, logging, and other system and application needs.

The formatter supports most C99 specifications, excluding:
* %Lf long double conversion
* wide character output

Kconfig options allow disabling features like floating-point
conversion if they are not necessary.  By default most conversions are
enabled.

The original z_vprintk() implementation is adapted to meet the
interface requirements of cbvprintf, and made available as an opt-in
feature for space-constrained applications that do not need full
formatting support.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
2020-11-13 06:38:01 -05:00