Check all errors in code?

[lovecreatesbea...]

Do you check all error conditions for all library calls in you code?

Is it necessary to check all errors? Is it convenient to check all
errors (or how to make code clean and readable with mass of non
business logic related code block)?

The following code from net-snmp library calls atoi five times but
checks none. Do we code a wrapper my_atoi_with_er ror_check() around
atoi and call this new one everywhere else? Is it a good practice (If
it is, why ANSI atoi doesn't do it)?

/* <quote file=../net-snmp-5.4.1.1/snmplib/vacm.c*/

286 char *
287 _vacm_parse_con fig_access_comm on(struct vacm_accessEntr y
**aptr, char *line)
288 {
289 struct vacm_accessEntr y access;
290 char *cPrefix = (char *) &access.context Prefix;
291 char *gName = (char *) &access.groupNa me;
292 size_t len;
293
294 access.status = atoi(line);
295 line = skip_token(line );
296 access.storageT ype = atoi(line);
297 line = skip_token(line );
298 access.security Model = atoi(line);
299 line = skip_token(line );
300 access.security Level = atoi(line);
301 line = skip_token(line );
302 access.contextM atch = atoi(line);
303 line = skip_token(line );
304 len = sizeof(access.g roupName);
305 line = read_config_rea d_octet_string( line, (u_char **)
&gName, &len);
306 len = sizeof(access.c ontextPrefix);
307 line = read_config_rea d_octet_string( line, (u_char **)
&cPrefix, &len);
308
309 *aptr = vacm_getAccessE ntry(access.gro upName,
310 access.contextP refix,
311 access.security Model,
312 access.security Level);
313 if (!*aptr)
314 *aptr = vacm_createAcce ssEntry(access. groupName,
315 access.contextP refix,
316 access.security Model,
317 access.security Level);
318 if (!*aptr)
319 return NULL;
320
321 (*aptr)->status = access.status;
322 (*aptr)->storageType = access.storageT ype;
323 (*aptr)->securityMode l = access.security Model;
324 (*aptr)->securityLeve l = access.security Level;
325 (*aptr)->contextMatch = access.contextM atch;
326 return line;
327 }

/* </quote*/

[Ian Collins]

lovecreatesbea. [e-mail] wrote:

Do you check all error conditions for all library calls in you code?

Is it necessary to check all errors? Is it convenient to check all
errors (or how to make code clean and readable with mass of non
business logic related code block)?

The following code from net-snmp library calls atoi five times but
checks none. Do we code a wrapper my_atoi_with_er ror_check() around
atoi and call this new one everywhere else? Is it a good practice (If
it is, why ANSI atoi doesn't do it)?

There is no way to check the result of atoi, that's why it's better to
use strtol in most situations.

--
Ian Collins.

[lovecreatesbea...]

On Sep 19, 4:08 pm, Ian Collins <[e-mail] mwrote:

lovecreatesbea. [e-mail] wrote:

Do you check all error conditions for all library calls in you code?

Is it necessary to check all errors? Is it convenient to check all
errors (or how to make code clean and readable with mass of non
business logic related code block)?

The following code from net-snmp library calls atoi five times but
checks none. Do we code a wrapper my_atoi_with_er ror_check() around
atoi and call this new one everywhere else? Is it a good practice (If
it is, why ANSI atoi doesn't do it)?

There is no way to check the result of atoi, that's why it's better to
use strtol in most situations.

I did not just mean check the return code from a function call.

Especially, I'm asking how to do complicated error check neatly.

[Richard Heathfield]

lovecreatesbea. [e-mail] said:

Do you check all error conditions for all library calls in you code?

It has been said that you should never check for a condition you don't know
how to handle. But apart from that, check everything.

Is it necessary to check all errors?

Is it useful to know whether your program worked? If not, then the program
itself is probably not all that useful.

The following code from net-snmp library calls atoi five times but
checks none.

Feel free to explain how you'd check atoi. Once you've failed to do that,
you will be in a position to explain why the code is broken.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Ian Collins]

lovecreatesbea. [e-mail] wrote:

On Sep 19, 4:08 pm, Ian Collins <[e-mail] mwrote:

>lovecreatesbea [e-mail] wrote:

>>Do you check all error conditions for all library calls in you code?
Is it necessary to check all errors? Is it convenient to check all
errors (or how to make code clean and readable with mass of non
business logic related code block)?
The following code from net-snmp library calls atoi five times but
checks none. Do we code a wrapper my_atoi_with_er ror_check() around
atoi and call this new one everywhere else? Is it a good practice (If
it is, why ANSI atoi doesn't do it)?

There is no way to check the result of atoi, that's why it's better to
use strtol in most situations.

I did not just mean check the return code from a function call.

Especially, I'm asking how to do complicated error check neatly.

Use a language with exceptions :)

--
Ian Collins.

[lovecreatesbea...]

On Sep 19, 4:08*pm, Ian Collins <[e-mail] mwrote:

lovecreatesbea. [e-mail] wrote:

Do you check all error conditions for all library calls in you code?

Is it necessary to check all errors? Is it convenient to check all
errors (or how to make code clean and readable with mass of non
business logic related code block)?

The following code from net-snmp library calls atoi five times but
checks none. Do we code a wrapper my_atoi_with_er ror_check() around
atoi and call this new one everywhere else? Is it a good practice (If
it is, why ANSI atoi doesn't do it)?

There is no way to check the result of atoi, that's why it's better to
use strtol in most situations.

I ever thought there're errno for atoi also. Thanks for reminder.

[Nick Keighley]

On 19 Sep, 09:16, "lovecreatesbea [e-mail]"
<lovecreatesbea [e-mail] ote:

On Sep 19, 4:08 pm, Ian Collins <[e-mail] mwrote:

lovecreatesbea. [e-mail] wrote:

Do you check all error conditions for all library calls in you code?

Is it necessary to check all errors? Is it convenient to check all
errors (or how to make code clean and readable with mass of non
business logic related code block)?

The following code from net-snmp library calls atoi five times but
checks none. Do we code a wrapper my_atoi_with_er ror_check() around
atoi and call this new one everywhere else? Is it a good practice (If
it is, why ANSI atoi doesn't do it)?

There is no way to check the result of atoi, that's why it's better to
use strtol in most situations.

I did not just mean check the return code from a function call.

Especially, I'm asking how to do complicated error check neatly.

as someone else suggested, use exceptions.

Out of interest I've coded simple TCP/IP applications
in both C and Python. The Python versions were shorter
and easier to follow.

I somtimes use an exception like style in C

Rv read_box (Db_handle dbh, Box* box, Box_id box_id)
{
Rv rv;
int i;

for (i = 1; i < SHELF_COUNT; i++)
{
if ((rv = read_shelf (dbh, box->shelf[i], box_id, i)) != OK)
return rv;
}

return OK;
}

This was wrappered in macros so the code looked more like:

Rv read_box (Db_handle dbh, Box* box, Box_id box_id)
{
int i;

for (i = 1; i < SHELF_COUNT; i++)
{
read_shelf (dbh, box->shelf[i], box_id, i);
CHECK_ERROR;
}

return OK;
}

It was reasonably easy to follow and reasonably
easy to verify that all the error checking was done.
--
Nick Keighley

"Object-oriented programming is an exceptionally bad idea
that could only have originated in California."
Dijkstra

[lovecreatesbea...]

On Sep 19, 4:28 pm, Richard Heathfield <[e-mail].i nvalidwrote:

lovecreatesbea. [e-mail] said:

Do you check all error conditions for all library calls in you code?

It has been said that you should never check for a condition you don't know
how to handle. But apart from that, check everything.

Sometimes, I omit some error check to come up with a can-work module
rapidly. Those error code will be supplied after some bug report
thrown out. This approach helps to catch up the schedule.

Is it necessary to check all errors?

Is it useful to know whether your program worked? If not, then the program
itself is probably not all that useful.

Thanks for being patient.

The following code from net-snmp library calls atoi five times but
checks none.

Feel free to explain how you'd check atoi. Once you've failed to do that,
you will be in a position to explain why the code is broken.

That snippet is radomly selected. They even do not check the malloc
for three times, see Line 55, 59 and 64 below.

Dude, was it you who wrote atoi piece plus this one?
/* <quote file=../net-snmp-5.4.1.1/agent/auto_nlist.c*/
34 long
35 auto_nlist_valu e(const char *string)
36 {
37 struct autonlist **ptr, *it = 0;
38 int cmp;
39
40 if (string == 0)
41 return 0;
42
43 ptr = &nlists;
44 while (*ptr != 0 && it == 0) {
45 cmp = strcmp((*ptr)->symbol, string);
46 if (cmp == 0)
47 it = *ptr;
48 else if (cmp < 0) {
49 ptr = &((*ptr)->left);
50 } else {
51 ptr = &((*ptr)->right);
52 }
53 }
54 if (*ptr == 0) {
55 *ptr = (struct autonlist *) malloc(sizeof(s truct
autonlist));
56 it = *ptr;
57 it->left = 0;
58 it->right = 0;
59 it->symbol = (char *) malloc(strlen(s tring) + 1);
60 strcpy(it->symbol, string);
61 /*
62 * allocate an extra byte for inclusion of a preceding
'_' later
63 */
64 it->nl[0].n_name = (char *) malloc(strlen(s tring) +
2);
65 #if defined(aix4) || defined(aix5)
66 strcpy(it->nl[0].n_name, string);
67 #else
68 sprintf(it->nl[0].n_name, "_%s", string);
69 #endif
70 it->nl[1].n_name = 0;
71 init_nlist(it->nl);
72 #if !(defined(aix4) || defined(aix5))
73 if (it->nl[0].n_type == 0) {
74 strcpy(it->nl[0].n_name, string);
75 init_nlist(it->nl);
76 }
77 #endif
78 if (it->nl[0].n_type == 0) {
79 if (!
netsnmp_ds_get_ boolean(NETSNMP _DS_APPLICATION _ID,
80
NETSNMP_DS_AGEN T_NO_ROOT_ACCES S)) {
81 snmp_log(LOG_ER R, "nlist err: neither %s nor _
%s found.\n",
82 string, string);
83 }
84 return (-1);
85 } else {
86 DEBUGMSGTL(("au to_nlist:auto_n list_value", "found
symbol %s at %x.\n",
87 it->symbol, it->nl[0].n_value));
88 return (it->nl[0].n_value);
89 }
90 } else
91 return (it->nl[0].n_value);
92 }

/* </quote*/

[Nick Keighley]

On 19 Sep, 09:54, "lovecreatesbea [e-mail]"
<lovecreatesbea [e-mail] ote:

On Sep 19, 4:28 pm, Richard Heathfield <[e-mail].i nvalidwrote:

lovecreatesbea. [e-mail] said:

Do you check all error conditions for all library calls in you code?

It has been said that you should never check for a condition you don't know
how to handle. But apart from that, check everything.

Sometimes, I omit some error check to come up with a can-work module
rapidly. Those error code will be supplied after some bug report
thrown out. This approach helps to catch up the schedule.

not in my experience! I'd much rather put the checks in at the
beginning.
And if you had the checks you wouldn't need to debug- your program
would tell you what was wrong.

<snip>

--
Nick Keighley

[lovecreatesbea...]

On Sep 19, 5:19*pm, Nick Keighley <nick_keighley_ nos...@hotmail. com>
wrote:

On 19 Sep, 09:54, "lovecreatesbea [e-mail]"

<lovecreatesbea [e-mail] ote:

On Sep 19, 4:28 pm, Richard Heathfield <[e-mail].i nvalidwrote:

lovecreatesbea. [e-mail] said:
Do you check all error conditions for all library calls in you code?

It has been said that you should never check for a condition you don't know
how to handle. But apart from that, check everything.

Sometimes, I omit some error check to come up with a can-work module
rapidly. Those error code will be supplied after some bug report
thrown out. This approach helps to catch up the schedule.

not in my experience! I'd much rather put the checks in at the
beginning.
And if you had the checks you wouldn't need to debug- your program
would tell you what was wrong.

Yes, your way is right way.