casaroli opened a new pull request, #21561:
URL: https://github.com/apache/nuttx/pull/21561
## Summary
`nuttx/compiler.h` reaches every program, and it defines the generic name
`object_size()` as a macro with two arguments. A program that has its own
`object_size()` with another number of arguments does not compile, for example
a C++ class with a member function `object_size()`.
With `NUTTX_NO_EXTENSIONS`, `nuttx/compiler.h` now removes `object_size()`
at its end and restores the program's own definition, as it does for
`memory_barrier()`, `UNUSED()` and the other helper macros.
`NOTE_PRINTF_OBJECT_SIZE()` in `nuttx/sched_note.h`, which `syslog()` of a
program can expand, uses `__builtin_object_size()` directly. The `_Generic` and
statement expressions around it need GCC or clang, which have the builtin.
## Impact
Only a program that defines `NUTTX_NO_EXTENSIONS` sees a change:
`object_size()` is not defined for it. NuttX code does not define
`NUTTX_NO_EXTENSIONS`, so the kernel, libc and apps build as before.
`NOTE_PRINTF_OBJECT_SIZE()` gives the same value as before with GCC and clang,
and other compilers cannot expand it before or after this change. No Kconfig
change, no ABI change.
`Documentation/os/libs/libc/index.rst` describes `NUTTX_NO_EXTENSIONS` with
"the helper macros of `nuttx/compiler.h` that the other headers do not use, for
example ...". This stays true, so the PR has no documentation change.
## Testing
A test program, `objsizename.c` (`NUTTX_NO_EXTENSIONS`, an `object_size()`
of its own with one argument, and `syslog()`), on `qemu-armv8a:knsh` (kernel
build, arm64, HVF): master does not compile it ("macro object_size requires 2
arguments"); this branch: 2 of 2 pass.
The same program with `SYSLOG_TO_SCHED_NOTE` and
`DRIVERS_NOTE_STRIP_FORMAT`, so that its `syslog()` expands
`NOTE_PRINTF_OBJECT_SIZE()`, compiled against the export of this branch: it
compiles. With the old `object_size()` line in `sched_note.h` it does not ("too
many arguments to function 'object_size'").
ostest on `qemu-armv8a:knsh` and `qemu-armv8a:nsh` (flat): exit status 0 on
both.
Compilers, by reading: the GCC section of `nuttx/compiler.h` already defined
`object_size()` as `__builtin_object_size()`. The other sections defined it as
`((size_t)-1)`, but they cannot expand `NOTE_PRINTF_ARG_TYPE()` (`_Generic`,
statement expressions, `&&label`), so `NOTE_PRINTF_OBJECT_SIZE()` reaches only
GCC and clang.
`tools/checkpatch.sh -c -u -m -g` passes.
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