awk: do not infinitely recurse getvar_s() if CONVFMT is set to a numeric value

function                                             old     new   delta
fmt_num                                              247     257     +10
evaluate                                            3385    3379      -6
getvar_s                                             111     102      -9
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 10/-15)             Total: -5 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 14 insertions, 6 deletions

diff --git a/editors/awk.c b/editors/awk.c
index ff6d6350b..8bc214b69 100644
--- a/editors/awk.c
+++ b/editors/awk.c
@@ -532,6 +532,7 @@ static const char vValues[] ALIGN1 =
         "%.6g\0"    "%.6g\0"    " \0"       " \0"
         "\n\0"      "\n\0"      "\0"        "\0"
         "\034\0"    "\0"        "\377";
+#define str_percent_dot_6g vValues
 
 /* hash size may grow to these values */
 #define FIRST_PRIME 61
@@ -922,7 +923,7 @@ static double my_strtod_or_hexoct(char **pp)
 
 /* -------- working with variables (set/get/copy/etc) -------- */
 
-static void fmt_num(const char *format, double n)
+static const char *fmt_num(const char *format, double n)
 {
         if (n == (long long)n) {
                 snprintf(g_buf, MAXVARFMT, "%lld", (long long)n);
@@ -939,6 +940,7 @@ static void fmt_num(const char *format, double n)
                         syntax_error(EMSG_INV_FMT);
                 }
         }
+        return g_buf;
 }
 
 static xhash *iamarray(var *a)
@@ -1025,8 +1027,15 @@ static const char *getvar_s(var *v)
 {
         /* if v is numeric and has no cached string, convert it to string */
         if ((v->type & (VF_NUMBER | VF_CACHED)) == VF_NUMBER) {
-                fmt_num(getvar_s(intvar[CONVFMT]), v->number);
-                v->string = xstrdup(g_buf);
+                const char *convfmt = str_percent_dot_6g; /* "%.6g" */
+                /* Get CONVFMT, unless we already recursed on it:
+                 * someone might try to cause stack overflow by setting
+                 * CONVFMT=9 (a numeric, not string, value)
+                 */
+                if (v != intvar[CONVFMT])
+                        convfmt = getvar_s(intvar[CONVFMT]);
+                /* Convert the value */
+                v->string = xstrdup(fmt_num(convfmt, v->number));
                 v->type |= VF_CACHED;
         }
         return (v->string == NULL) ? "" : v->string;
@@ -3097,9 +3106,8 @@ static var *evaluate(node *op, var *res)
                                         for (;;) {
                                                 var *v = evaluate(nextarg(&op1), TMPVAR0);
                                                 if (v->type & VF_NUMBER) {
-                                                        fmt_num(getvar_s(intvar[OFMT]),
-                                                                        getvar_i(v));
-                                                        fputs(g_buf, F);
+                                                        fputs(fmt_num(getvar_s(intvar[OFMT]), getvar_i(v)),
+                                                                F);
                                                 } else {
                                                         fputs(getvar_s(v), F);
                                                 }