Re: [PATCH 1/8] Add some helpers to manage the strings allocation/deallocation.

[Goffredo Baroncelli <kreijack@tiscalinet.it>]

Hi Eric,

On 02/25/2013 03:20 AM, Eric Sandeen wrote:
> On 2/23/13 7:46 AM, Goffredo Baroncelli wrote:
>> From: Goffredo Baroncelli <kreijack@inwind.it>
>>
>> This patch adds some helpers to manage the strings allocation and
>> deallocation.
>> The function string_list_add(char *) adds the passed string to a list;
>> the function string_list_free() frees all the strings together.
> 
> I have to say, I agree with Zach that there are more straightforward
> and less error-prone ways to accomplish this same result.
> 
> You said:
> 
>> your suggestion is not so easy applicable
> 
> to Zach's suggestion.  Why do you consider it to be not applicable?
> Maybe I am missing some subtlety, but it'd help if you could explain
> the problem that you see.

For example try on the following line (is a real example from the
function _cmd_disk_free):

   printf("Disk size:\t\t%*s\n", width,
        df_pretty_sizes(total_disk, mode));

it would be translated (note the '%*s'):

   if (mode == DF_HUMAN_UNIT)
	   printf("Disk size:\t\t%*s%s\n", width-2,
        	df_pretty_sizes_number(total_disk),
		df_pretty_sizes_unit(total_disk));
   else
	   printf("Disk size:\t\t%*lld\n", width, total_disk);


6 lines versus 2: does it make sense ?

> 
> I think that the asymmetry in i.e. _cmd_disk_free where you do:
> 
> +	printf("Disk size:\t\t%*s\n", width,
> +		df_pretty_sizes(total_disk, mode));
> <a few times>
> and then:
> 
> +	string_list_free();
> 
> ... because obviously (?)  "df_pretty_sizes" needs this cleanup ...
> 
> is unexpected, magic, and error-prone.

df_pretty_sizes is not a generic function. There is a reason because it
is _defined_static_. We could improve the function comment (or even
rename the function itself) to point out it better.
It is a facility to avoid to write a lot of equal lines.

However I am open to any suggestion which:
- let the code simple enough
- avoid the duplication of lines.

To avoid all this mess, we should add another conversion specifier with
the function register_printf_function(). Unfortunately I was not able to
find the equivalent one for sprintf().

BR
G.Baroncelli

> 
> -Eric
> 
> 
> 
> thanks,
> -Eric
> 
>> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
>> ---
>>  Makefile      |    3 ++-
>>  string_list.c |   63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  string_list.h |   23 +++++++++++++++++++++
>>  3 files changed, 88 insertions(+), 1 deletion(-)
>>  create mode 100644 string_list.c
>>  create mode 100644 string_list.h
>>
>> diff --git a/Makefile b/Makefile
>> index 596bf93..0d6c43a 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -5,7 +5,8 @@ objects = ctree.o disk-io.o radix-tree.o extent-tree.o print-tree.o \
>>  	  root-tree.o dir-item.o file-item.o inode-item.o \
>>  	  inode-map.o crc32c.o rbtree.o extent-cache.o extent_io.o \
>>  	  volumes.o utils.o btrfs-list.o btrfslabel.o repair.o \
>> -	  send-stream.o send-utils.o qgroup.o raid6.o
>> +	  send-stream.o send-utils.o qgroup.o raid6.o \
>> +	  string_list.o
>>  cmds_objects = cmds-subvolume.o cmds-filesystem.o cmds-device.o cmds-scrub.o \
>>  	       cmds-inspect.o cmds-balance.o cmds-send.o cmds-receive.o \
>>  	       cmds-quota.o cmds-qgroup.o cmds-replace.o
>> diff --git a/string_list.c b/string_list.c
>> new file mode 100644
>> index 0000000..8d8cc1f
>> --- /dev/null
>> +++ b/string_list.c
>> @@ -0,0 +1,63 @@
>> +/*
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public
>> + * License v2 as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public
>> + * License along with this program; if not, write to the
>> + * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
>> + * Boston, MA 021110-1307, USA.
>> + */
>> +
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +#include <unistd.h>
>> +
>> +/* To store the strings */
>> +static void **strings_to_free;
>> +static int count_string_to_free;
>> +
>> +/* 
>> + * Add a string to the dynamic allocated string list
>> + */
>> +char *string_list_add(char *s)
>> +{
>> +	int  size;
>> +
>> +	size = sizeof(void *) * ++count_string_to_free;
>> +	strings_to_free = realloc(strings_to_free, size);
>> +
>> +	/* if we don't have enough memory, we have more serius
>> +	   problem than that a wrong handling of not enough memory */
>> +	if (!strings_to_free) {
>> +		fprintf(stderr, "add_string_to_free(): Not enough memory\n");
>> +		count_string_to_free = 0;
>> +		return NULL;
>> +	}
>> +
>> +	strings_to_free[count_string_to_free-1] = s;
>> +	return s;
>> +}
>> +
>> +/*
>> + * Free the dynamic allocated strings list
>> + */
>> +void string_list_free()
>> +{
>> +	int	i;
>> +	for (i = 0 ; i < count_string_to_free ; i++)
>> +		free(strings_to_free[i]);
>> +
>> +	free(strings_to_free);
>> +
>> +	strings_to_free = 0;
>> +	count_string_to_free = 0;
>> +}
>> +
>> +
>> diff --git a/string_list.h b/string_list.h
>> new file mode 100644
>> index 0000000..f974fbc
>> --- /dev/null
>> +++ b/string_list.h
>> @@ -0,0 +1,23 @@
>> +/*
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public
>> + * License v2 as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public
>> + * License along with this program; if not, write to the
>> + * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
>> + * Boston, MA 021110-1307, USA.
>> + */
>> +
>> +#ifndef STRING_LIST_H
>> +#define STRING_LIST_H
>> +
>> +void string_list_add(char *s);
>> +void string_list_free();
>> +
>> +#endif
>>
> 
> 


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