[PATCH 1/3] jp: Fix segfaults during parameter expansion

[Joey Pabalinas <joeypabalinas@gmail.com>]

Running:

> $ zsh -fc ': ${${(PAA)p[foo]}::=x}'` in current zsh versions causes:
>
> [1] 4441 segmentation fault (core dumped) zsh -fc ': ${${(PAA)p[foo]}::=x}'

Also happens when testing with machabot:

> 19:42 <jp> > : ${${(PAA)p[foo]}::=x}
> 19:42 <machabot> jp: zsh[248]: segfault at 0 ip b7dfcda3 sp bfeb9ebc
>       error 4 in libc-2.13.so[b7d84000+149000]

Add a simple `dupstring(s2)` fallback instead of pointlessly
trying to concatenate `s2` to NULL and segfaulting.

Signed-off-by: Joey Pabalinas <joeypabalinas@gmail.com>

 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/Src/string.c b/Src/string.c
index 9e14ef94919c3e8ec5..038624d65a9f533494 100644
--- a/Src/string.c
+++ b/Src/string.c
@@ -144,8 +144,12 @@ dyncat(const char *s1, const char *s2)
 {
     /* This version always uses space from the current heap. */
     char *ptr;
-    size_t l1 = strlen(s1);
+    size_t l1;
 
+    /* String duplicate fallback to prevent NULL derefs */
+    if (!s1)
+	return dupstring(s2);
+    l1 = strlen(s1);
     ptr = (char *)zhalloc(l1 + strlen(s2) + 1);
     strcpy(ptr, s1);
     strcpy(ptr + l1, s2);
@@ -158,8 +162,12 @@ bicat(const char *s1, const char *s2)
 {
     /* This version always uses permanently-allocated space. */
     char *ptr;
-    size_t l1 = strlen(s1);
+    size_t l1;
 
+    /* String duplicate fallback to prevent NULL derefs */
+    if (!s1)
+	return dupstring(s2);
+    l1 = strlen(s1);
     ptr = (char *)zalloc(l1 + strlen(s2) + 1);
     strcpy(ptr, s1);
     strcpy(ptr + l1, s2);
-- 
2.15.1