From f3e5c7262e77ca84bcef60fe20a3dc70eae12d5e Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Mon, 11 Jan 2021 12:23:00 -0300 Subject: 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. --- posix/regexec.c | 75 ++++++++++----------------------------------------------- 1 file changed, 13 insertions(+), 62 deletions(-) diff --git a/posix/regexec.c b/posix/regexec.c index 889b10be9c..f7b4f9cfc3 100644 --- a/posix/regexec.c +++ b/posix/regexec.c @@ -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; } -- cgit 1.4.1