casaroli opened a new pull request, #21730:
URL: https://github.com/apache/nuttx/pull/21730
depends-on: apache/nuttx/pull/21729
## Summary
scanf() took the `L` length modifier as `l`. For `%Lf`, `%Le` and `%Lg` it
stored a double through a `long double *`. Where a long double is not a double
(arm64, RISC-V 64, x86_64), the value was wrong and the other bytes kept their
old value: `sscanf("3.75", "%Lf", &ld)` gave inf on arm64. Now `L` sets the
length of `ll`. A floating point conversion with it calls strtold() and stores
a long double, and an integer conversion (`%Ld`) stores a long long, as in GNU
libc. #21474 made the same change in printf().
The first commit only fixes the older nxstyle errors of lib_libvscanf.c (the
case labels of the switch statements), so that the check job can pass. The
object code does not change, with and without CONFIG_LIBC_FLOATINGPOINT
(compared on arm64). The last commit updates the lib_bscanf() note in
Documentation/os/libs/libc/stream.rst, which said that `%Lf` is not supported.
## Impact
- C library only, the same in flat, protected and kernel builds. Without
CONFIG_HAVE_LONG_DOUBLE the floating point conversions do not change.
- strtold() is in lib_strtold.c with strtod() and strtof(). That file is
built when LIBM_NONE is not set, and LIBC_FLOATINGPOINT depends on !LIBM_NONE,
so every configuration that compiles the new call has the function, with every
LIBM choice.
- Behavior: `%Ld`, `%Li`, `%Lu` and `%Lx` store a long long (they stored a
long, which is smaller on a 32-bit CPU), and `%llf` stores a long double, as in
GNU libc. lib_bscanf() with `%Lf` now fills a long double field of the
structure.
- Size of lib_libvscanf.o text: +152 bytes on arm64, +96 bytes on Cortex-M4
(stm32f4discovery:nsh with LIBC_FLOATINGPOINT), +92 bytes on mps2-an500:knsh.
The image text of qemu-armv8a:nsh grows by 8 bytes, and stm32f4discovery:nsh
does not change.
## Testing
Two test programs: ldprintf.c (15 cases of the `L` modifier in printf() and
scanf()) and printfld.c (long double in the printf and scanf families, and
strtold(); `sscanf`, `fscanf` and `vsscanf` with `%Lf`, `%Le`, `%Lg`, widths,
`%*Lf`, mixed arguments, and text read back).
- qemu-armv8a:knsh (kernel build), LIBC_FLOATINGPOINT and
LIBC_NUMBERED_ARGS: master ldprintf 2 failed (scanf, scanf-whole), printfld 120
passed, 30 failed; this branch ldprintf 0 failed, printfld 148 passed, 2
failed. ostest exits with status 0.
- qemu-armv8a:nsh (flat), the tests as built-in applications: master
ldprintf 2 failed, printfld 122 passed, 31 failed; this branch ldprintf 0
failed, printfld 151 passed, 2 failed. ostest exits with status 0.
- rv-virt:knsh64 (RISC-V 64, kernel build, TCG), LIBC_FLOATINGPOINT,
LIBC_NUMBERED_ARGS, ELF_STACKSIZE 8192: master ldprintf 2 failed, printfld 120
passed, 30 failed; this branch ldprintf 0 failed, printfld 148 passed, 2
failed. ostest exits with status 0.
- Not run: x86_64 (its 80-bit long double).
- The 2 cases that still fail are not in this PR: swprintf() of a long
double, and the value that scanf() stores after a failed conversion.
- Built, not run: stm32f4discovery:nsh with LIBC_FLOATINGPOINT (flat,
Cortex-M4) and mps2-an500:knsh with LIBC_FLOATINGPOINT (protected).
- `tools/checkpatch.sh -c -u -m -g` passes.
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