Re: [PATCH] net: Don't use nested functions to allow building with clang

[Leif Lindholm <leif@nuviainc.com>]

Hi Javier,

On Tue, May 19, 2020 at 10:34:22 +0200, Javier Martinez Canillas wrote:
> Nested functions are supported as an extension in GNU C, but are not in
> the clang compiler. Commit cb2f15c5448 ("normal/main: Search for specific
> config files for netboot") added a nested function which caused the build
> to break when compiling with clang.

Thanks for this. And apologies for bikeshedding (but since there is a
history with GRUB and nested functions, I will) - could we reword this
to make fewer references to clang? Nested functions are an abomination
not supported by the C language. I.e. something like.

---
net: break out nested function

Nested functions are not supported in C, but are permitted as an
extension in the GNU C dialect. Commit cb2f15c5448 ("normal/main:
Search for specific config files for netboot") added a nested function
which caused the build to break when compiling with clang.
Break that out into a static helper function to make the code portable
again.
---

> Reported-by: Daniel Axtens <dja@axtens.net>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
> ---
> 
>  grub-core/net/net.c | 65 +++++++++++++++++++++++----------------------
>  1 file changed, 33 insertions(+), 32 deletions(-)
> 
> diff --git a/grub-core/net/net.c b/grub-core/net/net.c
> index c42f0f4f71d..ec7e2899ed5 100644
> --- a/grub-core/net/net.c
> +++ b/grub-core/net/net.c
> @@ -1735,42 +1735,43 @@ grub_net_restore_hw (void)
>    return GRUB_ERR_NONE;
>  }
>  
> -grub_err_t
> -grub_net_search_config_file (char *config)
> +static int grub_config_search_through (char *config, char *suffix,

Style-wise, the function name should start in the first column on its
own line. (Running the file through gnu indent with default options
usually does the correct thing.)

/
    Leif

> +                                       grub_size_t num_tries,
> +                                       grub_size_t slice_size)
>  {
> -  grub_size_t config_len;
> -  char *suffix;
> +  while (num_tries-- > 0)
> +    {
> +      grub_file_t file;
>  
> -  auto int search_through (grub_size_t num_tries, grub_size_t slice_size);
> -  int search_through (grub_size_t num_tries, grub_size_t slice_size)
> -  {
> -    while (num_tries-- > 0)
> -      {
> -        grub_file_t file;
> +      grub_dprintf ("net", "attempt to fetch config %s\n", config);
>  
> -        grub_dprintf ("net", "attempt to fetch config %s\n", config);
> +      file = grub_file_open (config, GRUB_FILE_TYPE_CONFIG);
>  
> -        file = grub_file_open (config, GRUB_FILE_TYPE_CONFIG);
> +      if (file)
> +        {
> +          grub_file_close (file);
> +          return 0;
> +        }
> +      else
> +        {
> +          if (grub_errno == GRUB_ERR_IO)
> +            grub_errno = GRUB_ERR_NONE;
> +        }
>  
> -        if (file)
> -          {
> -            grub_file_close (file);
> -            return 0;
> -          }
> -        else
> -          {
> -            if (grub_errno == GRUB_ERR_IO)
> -              grub_errno = GRUB_ERR_NONE;
> -          }
> +      if (grub_strlen (suffix) < slice_size)
> +        break;
>  
> -        if (grub_strlen (suffix) < slice_size)
> -          break;
> +      config[grub_strlen (config) - slice_size] = '\0';
> +    }
>  
> -        config[grub_strlen (config) - slice_size] = '\0';
> -      }
> +  return 1;
> +}
>  
> -    return 1;
> -  }
> +grub_err_t
> +grub_net_search_config_file (char *config)
> +{
> +  grub_size_t config_len;
> +  char *suffix;
>  
>    config_len = grub_strlen (config);
>    config[config_len] = '-';
> @@ -1801,7 +1802,7 @@ grub_net_search_config_file (char *config)
>        if (client_uuid)
>          {
>            grub_strcpy (suffix, client_uuid);
> -          if (search_through (1, 0) == 0)
> +          if (grub_config_search_through (config, suffix, 1, 0) == 0)
>              return GRUB_ERR_NONE;
>          }
>  
> @@ -1816,7 +1817,7 @@ grub_net_search_config_file (char *config)
>          if (*ptr == ':')
>            *ptr = '-';
>  
> -      if (search_through (1, 0) == 0)
> +      if (grub_config_search_through (config, suffix, 1, 0) == 0)
>          return GRUB_ERR_NONE;
>  
>        /* By IP address */
> @@ -1831,7 +1832,7 @@ grub_net_search_config_file (char *config)
>                             ((n >> 24) & 0xff), ((n >> 16) & 0xff),      \
>                             ((n >> 8) & 0xff), ((n >> 0) & 0xff));
>  
> -            if (search_through (8, 1) == 0)
> +            if (grub_config_search_through (config, suffix, 8, 1) == 0)
>                return GRUB_ERR_NONE;
>              break;
>            }
> @@ -1848,7 +1849,7 @@ grub_net_search_config_file (char *config)
>                  *ptr = '-';
>  
>              grub_snprintf (suffix, GRUB_NET_MAX_STR_ADDR_LEN, "%s", buf);
> -            if (search_through (1, 0) == 0)
> +            if (grub_config_search_through (config, suffix, 1, 0) == 0)
>                return GRUB_ERR_NONE;
>              break;
>            }
> -- 
> 2.26.2
> 
> 
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