aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorGravatar Denys Vlasenko <vda.linux@googlemail.com>2020-12-21 10:09:48 +0100
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2020-12-21 10:14:18 +0100
commit07abc7c6f7dd0875e0aa548bba952174a54c8797 (patch)
tree88f42363939bfbf5221ed2e1f24eeb511ccc6721
parent901d2c3862e0aaf96fc38ab32bdf1aa3f7f509d2 (diff)
downloadbusybox-07abc7c6f7dd0875e0aa548bba952174a54c8797.tar.gz
busybox-07abc7c6f7dd0875e0aa548bba952174a54c8797.tar.bz2
hush: deal with FIXMEs for corner cases in parameter expansion
function old new delta expand_one_var 2323 2344 +21 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--shell/hush.c52
1 files changed, 34 insertions, 18 deletions
diff --git a/shell/hush.c b/shell/hush.c
index f29c985ad..a8f7237d5 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -6506,9 +6506,11 @@ static NOINLINE int expand_one_var(o_string *output, int n,
* Word is expanded to produce a glob pattern.
* Then var's value is matched to it and matching part removed.
*/
-//FIXME: ${x#...${...}...}
-//should evaluate inner ${...} even if x is "" and no shrinking of it is possible -
-//inner ${...} may have side effects!
+ /* bash compat: if x is "" and no shrinking of it is possible,
+ * inner ${...} is not evaluated. Example:
+ * unset b; : ${a%${b=B}}; echo $b
+ * assignment b=B only happens if $a is not "".
+ */
if (val && val[0]) {
char *t;
char *exp_exp_word;
@@ -6547,7 +6549,12 @@ static NOINLINE int expand_one_var(o_string *output, int n,
* and if // is used, it is encoded as \:
* var\pattern<SPECIAL_VAR_SYMBOL>repl<SPECIAL_VAR_SYMBOL>
*/
- if (val && val[0]) {
+ /* bash compat: if var is "", both pattern and repl
+ * are still evaluated, if it is unset, then not:
+ * unset b; a=; : ${a/z/${b=3}}; echo $b # b=3
+ * unset b; unset a; : ${a/z/${b=3}}; echo $b # b not set
+ */
+ if (val /*&& val[0]*/) {
/* pattern uses non-standard expansion.
* repl should be unbackslashed and globbed
* by the usual expansion rules:
@@ -6583,8 +6590,9 @@ static NOINLINE int expand_one_var(o_string *output, int n,
free(pattern);
free(repl);
} else {
- /* Empty variable always gives nothing */
- // "v=''; echo ${v/*/w}" prints "", not "w"
+ /* Unset variable always gives nothing */
+ // a=; echo ${a/*/w} # "w"
+ // unset a; echo ${a/*/w} # ""
/* Just skip "replace" part */
*p++ = SPECIAL_VAR_SYMBOL;
p = strchr(p, SPECIAL_VAR_SYMBOL);
@@ -6599,40 +6607,48 @@ static NOINLINE int expand_one_var(o_string *output, int n,
* var:N<SPECIAL_VAR_SYMBOL>M<SPECIAL_VAR_SYMBOL>
*/
arith_t beg, len;
+ unsigned vallen;
const char *errmsg;
beg = expand_and_evaluate_arith(exp_word, &errmsg);
if (errmsg)
- goto arith_err;
+ goto empty_result;
debug_printf_varexp("beg:'%s'=%lld\n", exp_word, (long long)beg);
*p++ = SPECIAL_VAR_SYMBOL;
exp_word = p;
p = strchr(p, SPECIAL_VAR_SYMBOL);
*p = '\0';
- len = expand_and_evaluate_arith(exp_word, &errmsg);
- if (errmsg)
- goto arith_err;
- debug_printf_varexp("len:'%s'=%lld\n", exp_word, (long long)len);
+ vallen = strlen(val);
if (beg < 0) {
/* negative beg counts from the end */
- beg = (arith_t)strlen(val) + beg;
- if (beg < 0) /* ${v: -999999} is "" */
- beg = len = 0;
+ beg = (arith_t)vallen + beg;
}
+ /* If expansion will be empty, do not even evaluate len */
+ if (!val || beg < 0 || beg > vallen) {
+ /* Why > vallen, not >=? bash:
+ * unset b; a=ab; : ${a:2:${b=3}}; echo $b # "", b=3 (!!!)
+ * unset b; a=a; : ${a:2:${b=3}}; echo $b # "", b not set
+ */
+ goto empty_result;
+ }
+ len = expand_and_evaluate_arith(exp_word, &errmsg);
+ if (errmsg)
+ goto empty_result;
+ debug_printf_varexp("len:'%s'=%lld\n", exp_word, (long long)len);
debug_printf_varexp("from val:'%s'\n", val);
if (len < 0) {
/* in bash, len=-n means strlen()-n */
- len = (arith_t)strlen(val) - beg + len;
+ len = (arith_t)vallen - beg + len;
if (len < 0) /* bash compat */
msg_and_die_if_script("%s: substring expression < 0", var);
}
- if (len <= 0 || !val || beg >= strlen(val)) {
- arith_err:
+ if (len <= 0 || !val /*|| beg >= vallen*/) {
+ empty_result:
val = NULL;
} else {
/* Paranoia. What if user entered 9999999999999
* which fits in arith_t but not int? */
- if (len >= INT_MAX)
+ if (len > INT_MAX)
len = INT_MAX;
val = to_be_freed = xstrndup(val + beg, len);
}