Hi Paul,
On Fri, Jul 19, 2024 at 02:53:38PM GMT, Alejandro Colomar wrote:
> strtol(3) doesn't set the end pointer if the base is invalid. This
> allows a caller to differentiate between "invalid base" (what
> strtoi(3bsd) calls EINVAL) and an "no digits seen" (what strtoi(3bsd)
> calls ECANCELED) in systems that report EINVAL on no digits seen (POSIX
> allows this).
>
> strtol("foo", &e, 0);
> strtol("0", &e, -1);
>
> The former call will set e = nptr.
> The latter will leave e untouched.
>
> The caller has no other way to portably differentiate the calls.
>
> The way to differentiate those, thus, is to initialize e = NULL, to
> allow reading it after the call.
>
> While doing this, change the behavior of this function to only set
> *endptr if strtol(3) has set it, leaving it untouched otherwise.
>
> Fixes: 034a18049cbc (2014-12-20, "assure: new module")
Self-correction: I had a typo while running git-blame(1), which led me
to not find that the assure() call already existed --as assert()--
before your commit, Paul.
It was actually introduced in 3af47ca3f67 (1994-12-20, ".").
Please amend the Fixes tags to:
Fixes: 3af47ca3f67 (1994-12-20, ".")
Fixes: 64ddc975e72c (2024-07-18, "xstrtol: document and stray less from
strtol")
Sorry for the confusion!
Cheers,
Alex
> Fixes: 64ddc975e72c (2024-07-18, "xstrtol: document and stray less from
> strtol")
> Cc: Paul Eggert <egg...@cs.ucla.edu>
> Cc: Bruno Haible <br...@clisp.org>
> Cc: Đoàn Trần Công Danh <congdan...@gmail.com>
> Cc: Eli Schwartz <eschwart...@gmail.com>
> Cc: Sam James <s...@gentoo.org>
> Cc: Serge Hallyn <se...@hallyn.com>
> Cc: Iker Pedrosa <ipedr...@redhat.com>
> Cc: Michael Vetter <jub...@iodoru.org>
> Cc: <lib...@lists.linux.dev>
> Signed-off-by: Alejandro Colomar <a...@kernel.org>
> ---
> lib/xstrtol.c | 35 +++++++++++++++++++++--------------
> 1 file changed, 21 insertions(+), 14 deletions(-)
>
> diff --git a/lib/xstrtol.c b/lib/xstrtol.c
> index c3145171f3..592673557f 100644
> --- a/lib/xstrtol.c
> +++ b/lib/xstrtol.c
> @@ -71,9 +71,7 @@ strtol_error
> __xstrtol (char const *nptr, char **endptr, int base,
> __strtol_t *val, char const *valid_suffixes)
> {
> - char *t_ptr;
> - char **p = endptr ? endptr : &t_ptr;
> - *p = (char *) nptr;
> + char *e = NULL;
>
> if (! TYPE_SIGNED (__strtol_t))
> {
> @@ -82,14 +80,21 @@ __xstrtol (char const *nptr, char **endptr, int base,
> while (isspace (ch))
> ch = *++q;
> if (ch == '-')
> - return LONGINT_INVALID;
> + {
> + if (endptr)
> + *endptr = (char *) nptr;
> + return LONGINT_INVALID;
> + }
> }
>
> errno = 0;
> - __strtol_t tmp = __strtol (nptr, p, base);
> + __strtol_t tmp = __strtol (nptr, &e, base);
> strtol_error err = LONGINT_OK;
>
> - if (*p == nptr)
> + if (endptr && e)
> + *endptr = e;
> +
> + if (e == nptr)
> {
> /* If there is no number but there is a valid suffix, assume the
> number is 1. The string is invalid otherwise. */
> @@ -113,19 +118,19 @@ __xstrtol (char const *nptr, char **endptr, int base,
> return err;
> }
>
> - if (**p != '\0')
> + if (*e != '\0')
> {
> int xbase = 1024;
> int suffixes = 1;
> strtol_error overflow;
>
> - if (!strchr (valid_suffixes, **p))
> + if (!strchr (valid_suffixes, *e))
> {
> *val = tmp;
> return err | LONGINT_INVALID_SUFFIX_CHAR;
> }
>
> - switch (**p)
> + switch (*e)
> {
> case 'E': case 'G': case 'g': case 'k': case 'K': case 'M': case 'm':
> case 'P': case 'Q': case 'R': case 'T': case 't': case 'Y': case 'Z':
> @@ -138,10 +143,10 @@ __xstrtol (char const *nptr, char **endptr, int base,
> power-of-1024. */
>
> if (strchr (valid_suffixes, '0'))
> - switch (p[0][1])
> + switch (e[1])
> {
> case 'i':
> - if (p[0][2] == 'B')
> + if (e[2] == 'B')
> suffixes += 2;
> break;
>
> @@ -153,7 +158,7 @@ __xstrtol (char const *nptr, char **endptr, int base,
> }
> }
>
> - switch (**p)
> + switch (*e)
> {
> case 'b':
> overflow = bkm_scale (&tmp, 512);
> @@ -224,8 +229,10 @@ __xstrtol (char const *nptr, char **endptr, int base,
> }
>
> err |= overflow;
> - *p += suffixes;
> - if (**p)
> + e += suffixes;
> + if (endptr)
> + *endptr = e;
> + if (*e)
> err |= LONGINT_INVALID_SUFFIX_CHAR;
> }
>
> --
> 2.45.2
>
--
<https://www.alejandro-colomar.es/>
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