[hackers] [sbase] expr: tonum: handle case where result was previously calculated || Randy Palamar

[git]

commit d335c366f7a2ef74ab8da19b721707110ec821c8
Author:     Randy Palamar <ra...@rnpnr.xyz>
AuthorDate: Mon Jan 22 14:18:10 2024 -0700
Commit:     Roberto E. Vargas Caballero <k...@shike2.com>
CommitDate: Wed Jan 31 05:00:51 2024 +0100

    expr: tonum: handle case where result was previously calculated
    
    As pointed out in a mail to dev expr was segfaulting when multiple
    math operations were specified on the command line: eg. 'expr 3 \*
    2 + 1'. This happens because the tonum(), introduced in e50d533,
    assumed that v->str was always non null. parse() guarantees this
    for user input but this is not the case when doop() is called with
    the result of a previous calculation. However in that case we know
    that v->num is already valid so we can simply return.

diff --git a/expr.c b/expr.c
index 3afb94b..044c6c1 100644
--- a/expr.c
+++ b/expr.c
@@ -21,7 +21,13 @@ static void
 tonum(struct val *v)
 {
        const char *errstr;
-       long long d = strtonum(v->str, LLONG_MIN, LLONG_MAX, &errstr);
+       long long d;
+
+       /* check if val is the result of an earlier calculation */
+       if (!v->str)
+               return;
+
+       d = strtonum(v->str, LLONG_MIN, LLONG_MAX, &errstr);
        if (errstr)
                enprintf(2, "error: expected integer, got %s\n", v->str);
        v->num = d;