linux-kernel - Re: [PATCH v2] getdents.2: Use appropriate types

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Date:   Thu, 29 Oct 2020 14:55:21 +0100
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Alejandro Colomar <colomar.6.4.3@...il.com>
Cc:     linux-man <linux-man@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "libc-alpha@...rceware.org" <libc-alpha@...rceware.org>
Subject: Re: [PATCH v2] getdents.2: Use appropriate types

Hi Alex,

On Thu, 29 Oct 2020 at 14:42, Alejandro Colomar <colomar.6.4.3@...il.com> wrote:
>
> getdents():
> This function has no glibc wrapper.
> As such, we should use the same types the Linux kernel uses:
> Use 'long' as the return type.
>
> getdents64():
> The glibc wrapper uses ssize_t for the return type,
> and 'size_t' for the count argument.

Take a look in the header file at the argument types for getdents64();
there's still some changes needed.

Thanks,

Michael


> Signed-off-by: Alejandro Colomar <colomar.6.4.3@...il.com>
> ---
>  man2/getdents.2 | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/man2/getdents.2 b/man2/getdents.2
> index a187fbcef..e14627e6e 100644
> --- a/man2/getdents.2
> +++ b/man2/getdents.2
> @@ -33,14 +33,14 @@
>  getdents, getdents64 \- get directory entries
>  .SH SYNOPSIS
>  .nf
> -.BI "int getdents(unsigned int " fd ", struct linux_dirent *" dirp ,
> +.BI "long getdents(unsigned int " fd ", struct linux_dirent *" dirp ,
>  .BI "             unsigned int " count );
>  .PP
>  .BR "#define _GNU_SOURCE" "        /* See feature_test_macros(7) */"
>  .B #include <dirent.h>
>  .PP
> -.BI "int getdents64(unsigned int " fd ", struct linux_dirent64 *" dirp ,
> -.BI "             unsigned int " count );
> +.BI "ssize_t getdents64(unsigned int " fd ", struct linux_dirent64 *" dirp ,
> +.BI "             size_t " count );
>  .fi
>  .PP
>  .IR Note :
> @@ -282,7 +282,8 @@ struct linux_dirent {
>  int
>  main(int argc, char *argv[])
>  {
> -    int fd, nread;
> +    int fd;
> +    long nread;
>      char buf[BUF_SIZE];
>      struct linux_dirent *d;
>      char d_type;
> @@ -301,7 +302,7 @@ main(int argc, char *argv[])
>
>          printf("\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- nread=%d \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\en", nread);
>          printf("inode#    file type  d_reclen  d_off   d_name\en");
> -        for (int bpos = 0; bpos < nread;) {
> +        for (long bpos = 0; bpos < nread;) {
>              d = (struct linux_dirent *) (buf + bpos);
>              printf("%8ld  ", d\->d_ino);
>              d_type = *(buf + bpos + d\->d_reclen \- 1);
> --
> 2.28.0
>


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/