Re: [PATCH] parser: don't keep alloca()ing in a loop for substitutions

[Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>]

наб <nabijaczleweli@xxxxxxxxxxxxxxxxxx> wrote:
>
> diff --git a/src/parser.c b/src/parser.c
> index a552c47..3f7e50a 100644
> --- a/src/parser.c
> +++ b/src/parser.c
> @@ -898,6 +898,7 @@ readtoken1(int firstc, char const *syntax, char *eofmark, int striptabs)
>        struct nodelist *bqlist;
>        int quotef;
>        int oldstyle;
> +       char *parsebackq_save;
>        /* syntax stack */
>        struct synstack synbase = { .syntax = syntax };
>        struct synstack *synstack = &synbase;
> @@ -906,6 +907,7 @@ readtoken1(int firstc, char const *syntax, char *eofmark, int striptabs)
>                synstack->dblquote = 1;
>        quotef = 0;
>        bqlist = NULL;
> +       parsebackq_save = NULL;
> 
>        STARTSTACKSTR(out);
>        loop: { /* for each line, until end of word */
> @@ -1355,15 +1357,18 @@ badsub:
> parsebackq: {
>        struct nodelist **nlpp;
>        union node *n;
> -       char *str;
> +       char *str, *mstr;
>        size_t savelen;
>        struct heredoc *saveheredoclist;
>        int uninitialized_var(saveprompt);
> 
> -       str = NULL;
> +       str = mstr = NULL;
>        savelen = out - (char *)stackblock();
>        if (savelen > 0) {
> -               str = alloca(savelen);
> +               if (savelen > 1024)
> +                       str = mstr = ckmalloc(savelen);
> +               else
> +                       str = parsebackq_save ?: (parsebackq_save = alloca(1024));
>                memcpy(str, stackblock(), savelen);
>        }
>         if (oldstyle) {
> @@ -1449,6 +1454,7 @@ done:
>        if (str) {
>                memcpy(out, str, savelen);
>                STADJUST(savelen, out);
> +               free(mstr);

You can't just call ckmalloc because that memory will be leaked
if there is a longjmp (such as sh_error) before you free it.

Cheers,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt