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getopt: merge from gnulib: alloca avoidance

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In one place, glibc's getopt uses alloca to construct a linked list of
possibilities for an "ambiguous" long option.  In gnulib, malloc
should be used instead.  Providing for both cases complicates things a
fair bit.  Instead of merging straight across, therefore, I have
chosen to rewrite it using a boolean vector instead of a linked list.
There is then only one allocation that might need freeing; in glibc it
can honor __libc_use_alloca as usual, and in gnulib we define
__libc_use_alloca to always be false, so we don't need ifdefs in the
middle of the function.  This should also be slightly more efficient
in the normal case of long options being fully spelled out -- I think
most people aren't even aware they _can_ sometimes abbreviate long
options.

One interesting consequence is that the list of possibilities is now
printed in exactly the order they appear in the list of long options,
instead of the first possibility being shuffled to the end.  This
shouldn't be a big deal but it did break one test that relied on the
exact text of this error message.

(The reason the previous patch was "in aid of" merging from gnulib is
I didn't want to have to make this change in two places.)

(The patch looks bigger than it really is because there's a fair bit
of reindentation and code rearrangement.)

	* posix/getopt.c: When used standalone, define __libc_use_alloca
	as always false and alloca to abort if called.
	(process_long_option): Rewrite handling of ambiguous long options
	to use a single boolean vector, not a linked list; use
	__libc_use_alloca to decide whether to allocate this using alloca.

	* posix/tst-getopt_long1.c: Adjust text of expected error message.
This commit is contained in:
Zack Weinberg 2017-04-01 17:13:45 -04:00
parent dfbea09f96
commit aeacb9f912
3 changed files with 164 additions and 124 deletions
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7
ChangeLog
View File

@ -1,5 +1,12 @@
2017-04-07 Zack Weinberg <zackw@panix.com>
* posix/getopt.c: When used standalone, define __libc_use_alloca
as always false and alloca to abort if called.
(process_long_option): Rewrite handling of ambiguous long options
to use a single boolean vector, not a linked list; use
__libc_use_alloca to decide whether to allocate this using alloca.
* posix/tst-getopt_long1.c: Adjust text of expected error message.
* posix/getopt.c (process_long_option): New function split out
from _getopt_internal_r.
(_getopt_internal_r): Replace both copies of the long-option

201
posix/getopt.c
View File

@ -51,6 +51,10 @@
# define flockfile(fp) /* nop */
# define funlockfile(fp) /* nop */
# endif
/* When used standalone, do not attempt to use alloca. */
# define __libc_use_alloca(size) 0
# undef alloca
# define alloca(size) (abort (), (void *)0)
#endif
/* This implementation of 'getopt' has three modes for handling
@ -197,33 +201,37 @@ process_long_option (int argc, char **argv, const char *optstring,
size_t namelen;
const struct option *p;
const struct option *pfound = NULL;
struct option_list
{
const struct option *p;
struct option_list *next;
} *ambig_list = NULL;
int exact = 0;
int indfound = -1;
int n_options;
int option_index;
for (nameend = d->__nextchar; *nameend && *nameend != '='; nameend++)
/* Do nothing. */ ;
namelen = nameend - d->__nextchar;
/* Test all long options for either exact match
or abbreviated matches. */
for (p = longopts, option_index = 0; p->name; p++, option_index++)
if (!strncmp (p->name, d->__nextchar, namelen))
{
if (namelen == strlen (p->name))
/* First look for an exact match, counting the options as a side
effect. */
for (p = longopts, n_options = 0; p->name; p++, n_options++)
if (!strncmp (p->name, d->__nextchar, namelen)
&& namelen == strlen (p->name))
{
/* Exact match found. */
pfound = p;
indfound = option_index;
exact = 1;
option_index = n_options;
break;
}
else if (pfound == NULL)
if (pfound == NULL)
{
/* Didn't find an exact match, so look for abbreviations. */
unsigned char *ambig_set = NULL;
int ambig_malloced = 0;
int ambig_fallback = 0;
int indfound = -1;
for (p = longopts, option_index = 0; p->name; p++, option_index++)
if (!strncmp (p->name, d->__nextchar, namelen))
{
if (pfound == NULL)
{
/* First nonexact match found. */
pfound = p;
@ -235,94 +243,73 @@ process_long_option (int argc, char **argv, const char *optstring,
|| pfound->val != p->val)
{
/* Second or later nonexact match found. */
struct option_list *newp = alloca (sizeof (*newp));
newp->p = p;
newp->next = ambig_list;
ambig_list = newp;
if (!ambig_fallback)
{
if (!print_errors)
/* Don't waste effort tracking the ambig set if
we're not going to print it anyway. */
ambig_fallback = 1;
else if (!ambig_set)
{
if (__libc_use_alloca (n_options))
ambig_set = alloca (n_options);
else if ((ambig_set = malloc (n_options)) == NULL)
/* Fall back to simpler error message. */
ambig_fallback = 1;
else
ambig_malloced = 1;
if (ambig_set)
{
memset (ambig_set, 0, n_options);
ambig_set[indfound] = 1;
}
}
if (ambig_set)
ambig_set[option_index] = 1;
}
}
}
if (ambig_list != NULL && !exact)
if (ambig_set || ambig_fallback)
{
if (print_errors)
{
struct option_list first;
first.p = pfound;
first.next = ambig_list;
ambig_list = &first;
flockfile (stderr);
fprintf (stderr, _("%s: option '%s' is ambiguous; possibilities:"),
argv[0], argv[d->optind]);
do
if (ambig_fallback)
fprintf (stderr, _("%s: option '%s%s' is ambiguous\n"),
argv[0], prefix, d->__nextchar);
else
{
fprintf (stderr, " '--%s'", ambig_list->p->name);
ambig_list = ambig_list->next;
}
while (ambig_list != NULL);
flockfile (stderr);
fprintf (stderr,
_("%s: option '%s%s' is ambiguous; possibilities:"),
argv[0], prefix, d->__nextchar);
/* This must use 'fprintf' even though it's only printing a
single character, so that it goes through __fxprintf_nocancel
when compiled as part of glibc. */
for (option_index = 0; option_index < n_options; option_index++)
if (ambig_set[option_index])
fprintf (stderr, " '%s%s'",
prefix, longopts[option_index].name);
/* This must use 'fprintf' even though it's only
printing a single character, so that it goes through
__fxprintf_nocancel when compiled as part of glibc. */
fprintf (stderr, "\n");
funlockfile (stderr);
}
}
if (ambig_malloced)
free (ambig_set);
d->__nextchar += strlen (d->__nextchar);
d->optind++;
d->optopt = 0;
return '?';
}
if (pfound != NULL)
{
option_index = indfound;
d->optind++;
if (*nameend)
{
/* Don't test has_arg with >, because some C compilers don't
allow it to be used on enums. */
if (pfound->has_arg)
d->optarg = nameend + 1;
else
{
if (print_errors)
fprintf (stderr,
_("%s: option '%s%s' doesn't allow an argument\n"),
argv[0], prefix, pfound->name);
d->__nextchar += strlen (d->__nextchar);
d->optopt = pfound->val;
return '?';
}
}
else if (pfound->has_arg == 1)
{
if (d->optind < argc)
d->optarg = argv[d->optind++];
else
{
if (print_errors)
fprintf (stderr,
_("%s: option '%s%s' requires an argument\n"),
argv[0], prefix, pfound->name);
d->__nextchar += strlen (d->__nextchar);
d->optopt = pfound->val;
return optstring[0] == ':' ? ':' : '?';
}
}
d->__nextchar += strlen (d->__nextchar);
if (longind != NULL)
*longind = option_index;
if (pfound->flag)
{
*(pfound->flag) = pfound->val;
return 0;
}
return pfound->val;
}
if (pfound == NULL)
{
/* Can't find it as a long option. If this is not getopt_long_only,
or the option starts with '--' or is not a valid short option,
then it's an error. */
@ -343,6 +330,52 @@ process_long_option (int argc, char **argv, const char *optstring,
return -1;
}
/* We have found a matching long option. Consume it. */
d->optind++;
d->__nextchar = NULL;
if (*nameend)
{
/* Don't test has_arg with >, because some C compilers don't
allow it to be used on enums. */
if (pfound->has_arg)
d->optarg = nameend + 1;
else
{
if (print_errors)
fprintf (stderr,
_("%s: option '%s%s' doesn't allow an argument\n"),
argv[0], prefix, pfound->name);
d->optopt = pfound->val;
return '?';
}
}
else if (pfound->has_arg == 1)
{
if (d->optind < argc)
d->optarg = argv[d->optind++];
else
{
if (print_errors)
fprintf (stderr,
_("%s: option '%s%s' requires an argument\n"),
argv[0], prefix, pfound->name);
d->optopt = pfound->val;
return optstring[0] == ':' ? ':' : '?';
}
}
if (longind != NULL)
*longind = option_index;
if (pfound->flag)
{
*(pfound->flag) = pfound->val;
return 0;
}
return pfound->val;
}
/* Initialize internal data upon the first call to getopt. */
static const char *

2
posix/tst-getopt_long1.c
View File

@ -56,7 +56,7 @@ do_test (void)
printf ("message = \"%s\"\n", line);
static const char expected[] = "\
program: option '--on' is ambiguous; possibilities: '--one' '--onto' '--one-one'\n";
program: option '--on' is ambiguous; possibilities: '--one' '--one-one' '--onto'\n";
return c != '?' || strcmp (line, expected) != 0;
}