[PATCH v1 1/2] xstrtol: Correctly handle an invalid base

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From: Alejandro Colomar <[email protected]>
To: [email protected]
Cc: Alejandro Colomar <[email protected]>, Paul Eggert <[email protected]>, 
	Bruno Haible <[email protected]>, 
	=?utf-8?B?xJBvw6BuIFRy4bqnbiBDw7RuZw==?= Danh <[email protected]>, Eli Schwartz <[email protected]>, Sam James <[email protected]>, 
	Serge Hallyn <[email protected]>, Iker Pedrosa <[email protected]>, 
	Michael Vetter <[email protected]>, [email protected]
Subject: [PATCH v1 1/2] xstrtol: Correctly handle an invalid base
References: <[email protected]>
MIME-Version: 1.0
In-Reply-To: <[email protected]>

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 =3D 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 =3D 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")
Fixes: 64ddc975e72c (2024-07-18, "xstrtol: document and stray less from str=
tol")
Cc: Paul Eggert <[email protected]>
Cc: Bruno Haible <[email protected]>
Cc: =C4=90o=C3=A0n Tr=E1=BA=A7n C=C3=B4ng Danh <[email protected]>
Cc: Eli Schwartz <[email protected]>
Cc: Sam James <[email protected]>
Cc: Serge Hallyn <[email protected]>
Cc: Iker Pedrosa <[email protected]>
Cc: Michael Vetter <[email protected]>
Cc: <[email protected]>
Signed-off-by: Alejandro Colomar <[email protected]>
---
 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 =3D endptr ? endptr : &t_ptr;
-  *p =3D (char *) nptr;
+  char *e =3D NULL;
=20
   if (! TYPE_SIGNED (__strtol_t))
     {
@@ -82,14 +80,21 @@ __xstrtol (char const *nptr, char **endptr, int base,
       while (isspace (ch))
         ch =3D *++q;
       if (ch =3D=3D '-')
-        return LONGINT_INVALID;
+        {
+          if (endptr)
+            *endptr =3D (char *) nptr;
+          return LONGINT_INVALID;
+        }
     }
=20
   errno =3D 0;
-  __strtol_t tmp =3D __strtol (nptr, p, base);
+  __strtol_t tmp =3D __strtol (nptr, &e, base);
   strtol_error err =3D LONGINT_OK;
=20
-  if (*p =3D=3D nptr)
+  if (endptr && e)
+    *endptr =3D e;
+
+  if (e =3D=3D 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;
     }
=20
-  if (**p !=3D '\0')
+  if (*e !=3D '\0')
     {
       int xbase =3D 1024;
       int suffixes =3D 1;
       strtol_error overflow;
=20
-      if (!strchr (valid_suffixes, **p))
+      if (!strchr (valid_suffixes, *e))
         {
           *val =3D tmp;
           return err | LONGINT_INVALID_SUFFIX_CHAR;
         }
=20
-      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.  */
=20
           if (strchr (valid_suffixes, '0'))
-            switch (p[0][1])
+            switch (e[1])
               {
               case 'i':
-                if (p[0][2] =3D=3D 'B')
+                if (e[2] =3D=3D 'B')
                   suffixes +=3D 2;
                 break;
=20
@@ -153,7 +158,7 @@ __xstrtol (char const *nptr, char **endptr, int base,
               }
         }
=20
-      switch (**p)
+      switch (*e)
         {
         case 'b':
           overflow =3D bkm_scale (&tmp, 512);
@@ -224,8 +229,10 @@ __xstrtol (char const *nptr, char **endptr, int base,
         }
=20
       err |=3D overflow;
-      *p +=3D suffixes;
-      if (**p)
+      e +=3D suffixes;
+      if (endptr)
+        *endptr =3D e;
+      if (*e)
         err |=3D LONGINT_INVALID_SUFFIX_CHAR;
     }
=20
--=20
2.45.2


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