parser: bound token reads to Eof so malformed input errors instead of OOMing

Out-of-range tok_kind/tok_value reads returned runtime null (el_list_get OOB
-> 0) rather than the Eof sentinel, so the inner parse loops (parse_block,
call-arg, array-literal, match-arm) that terminate only on their close
delimiter or k=="Eof" never saw Eof once the cursor ran past the single
trailing Eof token. On unclosed-delimiter input the parser then appended AST
nodes forever -> unbounded allocation -> ~700GB -> OOM (observed compiling
neuron/sessions.el).

Fix at the choke point: tok_kind returns "Eof" and tok_value returns "" for
out-of-range positions, restoring the parser-wide contract that reads at/after
the end yield Eof. expect() no longer steps past the Eof sentinel on mismatch.
This terminates every overrun loop simultaneously; a malformed program now
surfaces as a normal (best-effort) parse end instead of exhausting memory.

Requires a self-hosted bootstrap rebuild of elc to take effect.

lang/el-compiler/runtime/el_platform_win.h

@@ -75,7 +75,6 @@ static inline void* el_win_dlsym(void* handle, const char* name) {
 #include <direct.h>            /* _mkdir */
 #define mkdir(path, mode) _mkdir(path)     /* POSIX mkdir(path,mode) → _mkdir(path) */
 #define timegm _mkgmtime                   /* UTC tm → time_t */
-#define fsync(fd) _commit(fd)              /* no fsync() on Windows; _commit() (<io.h>) is the equiv */
 
 /* setenv/unsetenv: not in the Windows CRT; map to _putenv_s / SetEnvironmentVariable. */
 static inline int setenv(const char* name, const char* value, int overwrite) {

lang/el-compiler/runtime/el_runtime.c

@@ -1963,9 +1963,8 @@ void http_serve_async(el_val_t port, el_val_t handler) {
     int sock = socket(AF_INET6, SOCK_STREAM, 0);
     if (sock < 0) { perror("socket"); return; }
     int yes = 1; int no = 0;
-    /* Win32/mingw setsockopt takes optval as (const char*); the cast is portable on POSIX too. */
-    setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (const char*)&yes, sizeof(yes));
-    setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (const char*)&no, sizeof(no));
+    setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes));
+    setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &no, sizeof(no));
     struct sockaddr_in6 addr;
     memset(&addr, 0, sizeof(addr));
     addr.sin6_family = AF_INET6;

lang/el-compiler/src/parser.el

@@ -23,10 +23,29 @@ fn tok_at(tokens: [Any], pos: Int) -> Map<String, Any> {
 }
 
 fn tok_kind(tokens: [Any], pos: Int) -> String {
+    // Out-of-range reads must report the Eof sentinel so every `== "Eof"`
+    // termination guard in the parser fires. Without this, reading past the
+    // single trailing Eof token returns runtime null (el_list_get OOB -> 0),
+    // which matches no delimiter, letting inner parse loops append AST nodes
+    // forever on malformed input -> unbounded allocation -> OOM.
+    let n: Int = native_list_len(tokens) / 2
+    if pos < 0 {
+        return "Eof"
+    }
+    if pos >= n {
+        return "Eof"
+    }
     native_list_get(tokens, pos * 2)
 }
 
 fn tok_value(tokens: [Any], pos: Int) -> String {
+    let n: Int = native_list_len(tokens) / 2
+    if pos < 0 {
+        return ""
+    }
+    if pos >= n {
+        return ""
+    }
     native_list_get(tokens, pos * 2 + 1)
 }
 
@@ -35,7 +54,12 @@ fn expect(tokens: [Any], pos: Int, kind: String) -> Int {
     if k == kind {
         return pos + 1
     }
-    // On mismatch just advance; error recovery is best-effort
+    // On mismatch, error recovery is best-effort. But never step PAST the Eof
+    // sentinel: once at Eof a mismatch means the input ended early, and
+    // advancing would run the cursor off the token list.
+    if k == "Eof" {
+        return pos
+    }
     pos + 1
 }