include/stdio.h: Hide the kernel file system types from kernel-build programs.

[casaroli]

Summary

stdio.h includes nuttx/fs/fs.h and nuttx/lib/lib.h. So every program that includes stdio.h also sees the kernel's struct file, struct inode and the other file system types. A program that defines its own struct file does not compile: error: redefinition of 'struct file'.

In the user space of a kernel build (CONFIG_BUILD_KERNEL and not __KERNEL__), programs cannot use those types. This PR makes stdio.h stop including the two headers there. Kernel code, and flat and protected builds, still get them. Removing them for every build breaks many files that rely on the indirect includes.

stdio.h itself needs only the FILE name, the fopencookie() callback types and lib_get_stream() (which stdin, stdout and stderr expand to). FILE stays an incomplete type, stdio.h declares lib_get_stream(), and the cookie types move from fs.h to a new nuttx/fs/cookie.h that both stdio.h and fs.h include.

The libc files that are built for user space and used kernel types or other headers through stdio.h now include what they use.

The first commit fixes the old nxstyle errors in three of the touched files, with no code change: the object code of the three files is identical before and after (qemu-armv8a:nsh with CONFIG_LIBC_LOCALE).

Impact

Programs of a kernel build that used kernel file system types or nuttx/lib/lib.h macros through stdio.h must include those headers themselves. Flat and protected builds, and kernel code, do not change.

The commit "include/nuttx/tls.h: Move the stream structures from nuttx/fs/fs.h." moves struct file_struct, struct streamlist and the __FS_FLAG_* stream flags from nuttx/fs/fs.h to nuttx/tls.h, where struct task_info_s holds the stream list (review). fs.h no longer includes nuttx/fs/cookie.h.

The nxstyle commit makes nxstyle accept an #include inside an initializer. lib_iconv.c includes its code page tables that way, so CI failed on 8 old warnings (#include outside of 'Included Files' section) as soon as the PR touched the file. Over all C files of the tree, the only warnings that go away are these 8 and the same ones in syscall_names.c and syscall_stublookup.c. No new warning appears.

Testing

A program that defines its own struct file and includes <stdio.h>, built outside the tree against the qemu-armv8a:knsh export package and run in QEMU 11:

Before:

ownfile.c:5:8: error: redefinition of 'struct file'

After:

nsh> ownfile
ownfile: struct file value 42

Kernel builds with -Wno-cpp -Werror, each followed by make export and the apps make import (all apps of the configuration compiled for user space): qemu-armv8a:knsh, imx93-evk:knsh, qemu-armv7a:knsh, sabre-6quad:netknsh, sama5d4-ek:knsh, rv-virt:knsh, rv-virt:knsh64, rv-virt:ksmp64, rv-virt:knsh_paging, rv-virt:knetnsh64, rv-virt:kfb64, icicle:knsh, canmv230:knsh, esp32s3-devkit:kernel_n8r2.

The apps import needs apache/nuttx-apps#3820 and apache/nuttx-apps#3823 (both merged), which add includes that some apps files took from stdio.h indirectly.

Flat builds with -Wno-cpp -Werror, size unchanged: lm3s6965-ek:qemu-flat, mps2-an500:nsh.

After the stream structures moved to nuttx/tls.h, with -Wno-cpp -Werror: qemu-armv8a:knsh, rv-virt:knetnsh64 and sabre-6quad:netknsh (each with make export and the apps make import), qemu-armv7a:knsh, rv-virt:knsh64, lm3s6965-ek:qemu-flat, lm3s6965-ek:qemu-protected, mps2-an500:nsh, esp32-devkitc:nsh, qemu-armv8a:nsh.

tools/checkpatch.sh -c -u -m -g passes.

[github-actions]

MemBrowse Memory Report

qemu-armv8a

• Code: .text.init_builtin_run +60 B (+0.0%, 347,480 B)

qemu-intel64

• Code: .text +74 B (+0.0%, 8,682,514 B)
  No memory changes detected for:
• arduino-mega2560
• esp32-devkitc
• hifive1-revb
• mirtoo
• rx65n-rsk2mb
• s698pm-dkit
• stm32-nucleo-f103rb

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• nshlib, testing/ostest: Include the headers that are used. nuttx-apps#3820 @ 2473ef82a4
• netutils/codecs: Include errno.h in md5.c. nuttx-apps#3823 @ 722c63c531

CI run: https://github.com/apache/nuttx/actions/runs/37943764063

[xiaoxiang781216]

it's better to move cookie_io_functions_t and struct file_struct to stdio.h and struct streamlist to include/nuttx/tls_task.h.

[casaroli]

Done for struct file_struct and struct streamlist: both are now in nuttx/tls.h with the stream flags (I think you meant tls.h, next to ta_streamlist), and fs.h no longer has them. I also tried moving cookie_io_functions_t and its callback types to stdio.h, but that does not build: for kernel code and flat builds, stdio.h includes nuttx/lib/lib.h, which reaches nuttx/tls.h (lib.h → kmalloc.h → sched.h → tls.h) before stdio.h can define the types, and struct file_struct needs them. So they stay in the small nuttx/fs/cookie.h that both stdio.h and tls.h include. FILE stays an incomplete type in stdio.h.

[xiaoxiang781216]

why add?

[casaroli]

stdin, stdout and stderr expand to lib_get_stream(), which is declared in nuttx/lib/lib.h. stdio.h no longer includes that header for the programs of a kernel build, so it declares the function itself.