regexec: remove alloca usage in build_trtable

It syncs with gnulib version 1731fef3d.  On build_trtable prevent
inlining, so that it doesn't bloat the caller's stack and use auto
variables instead of alloca/malloc.

After these changes, build_trtable's total stack allocation is
only 20 KiB on a 64-bit machine, and this is less than glibc's 64
KiB cutoff so there's little point to using alloca to shrink it.

Checked on x86_64-linux-gnu.
This commit is contained in:
Adhemerval Zanella 2021-01-11 12:23:00 -03:00
parent f0908ba118
commit f3e5c7262e

View File

@ -3247,7 +3247,7 @@ expand_bkref_cache (re_match_context_t *mctx, re_node_set *cur_nodes,
/* Build transition table for the state.
Return true if successful. */
static bool
static bool __attribute_noinline__
build_trtable (const re_dfa_t *dfa, re_dfastate_t *state)
{
reg_errcode_t err;
@ -3255,36 +3255,20 @@ build_trtable (const re_dfa_t *dfa, re_dfastate_t *state)
int ch;
bool need_word_trtable = false;
bitset_word_t elem, mask;
bool dests_node_malloced = false;
bool dest_states_malloced = false;
Idx ndests; /* Number of the destination states from 'state'. */
re_dfastate_t **trtable;
re_dfastate_t **dest_states = NULL, **dest_states_word, **dest_states_nl;
re_node_set follows, *dests_node;
bitset_t *dests_ch;
re_dfastate_t *dest_states[SBC_MAX];
re_dfastate_t *dest_states_word[SBC_MAX];
re_dfastate_t *dest_states_nl[SBC_MAX];
re_node_set follows;
bitset_t acceptable;
struct dests_alloc
{
re_node_set dests_node[SBC_MAX];
bitset_t dests_ch[SBC_MAX];
} *dests_alloc;
/* We build DFA states which corresponds to the destination nodes
from 'state'. 'dests_node[i]' represents the nodes which i-th
destination state contains, and 'dests_ch[i]' represents the
characters which i-th destination state accepts. */
if (__libc_use_alloca (sizeof (struct dests_alloc)))
dests_alloc = (struct dests_alloc *) alloca (sizeof (struct dests_alloc));
else
{
dests_alloc = re_malloc (struct dests_alloc, 1);
if (__glibc_unlikely (dests_alloc == NULL))
return false;
dests_node_malloced = true;
}
dests_node = dests_alloc->dests_node;
dests_ch = dests_alloc->dests_ch;
re_node_set dests_node[SBC_MAX];
bitset_t dests_ch[SBC_MAX];
/* Initialize transition table. */
state->word_trtable = state->trtable = NULL;
@ -3294,8 +3278,6 @@ build_trtable (const re_dfa_t *dfa, re_dfastate_t *state)
ndests = group_nodes_into_DFAstates (dfa, state, dests_node, dests_ch);
if (__glibc_unlikely (ndests <= 0))
{
if (dests_node_malloced)
re_free (dests_alloc);
/* Return false in case of an error, true otherwise. */
if (ndests == 0)
{
@ -3310,38 +3292,14 @@ build_trtable (const re_dfa_t *dfa, re_dfastate_t *state)
err = re_node_set_alloc (&follows, ndests + 1);
if (__glibc_unlikely (err != REG_NOERROR))
goto out_free;
/* Avoid arithmetic overflow in size calculation. */
size_t ndests_max
= ((SIZE_MAX - (sizeof (re_node_set) + sizeof (bitset_t)) * SBC_MAX)
/ (3 * sizeof (re_dfastate_t *)));
if (__glibc_unlikely (ndests_max < ndests))
goto out_free;
if (__libc_use_alloca ((sizeof (re_node_set) + sizeof (bitset_t)) * SBC_MAX
+ ndests * 3 * sizeof (re_dfastate_t *)))
dest_states = (re_dfastate_t **)
alloca (ndests * 3 * sizeof (re_dfastate_t *));
else
{
dest_states = re_malloc (re_dfastate_t *, ndests * 3);
if (__glibc_unlikely (dest_states == NULL))
{
out_free:
if (dest_states_malloced)
re_free (dest_states);
re_node_set_free (&follows);
for (i = 0; i < ndests; ++i)
re_node_set_free (dests_node + i);
if (dests_node_malloced)
re_free (dests_alloc);
return false;
}
dest_states_malloced = true;
out_free:
re_node_set_free (&follows);
for (i = 0; i < ndests; ++i)
re_node_set_free (dests_node + i);
return false;
}
dest_states_word = dest_states + ndests;
dest_states_nl = dest_states_word + ndests;
bitset_empty (acceptable);
/* Then build the states for all destinations. */
@ -3466,16 +3424,9 @@ out_free:
}
}
if (dest_states_malloced)
re_free (dest_states);
re_node_set_free (&follows);
for (i = 0; i < ndests; ++i)
re_node_set_free (dests_node + i);
if (dests_node_malloced)
re_free (dests_alloc);
return true;
}