Initialize required global variables to avoid compilation failure

In dynamic linking mode, the bootstrapping process will fail, and the
root cause is that certain global variables are uninitialized, causing
the compiler to retrieve invalid values and trigger a segmentation
fault.

After further experiments, this commit initializes minimal required
variables so that the bootstrapping can complete in both static and
dynamic modes.

Author: DrXiao

src/elf.c

@@ -11,7 +11,7 @@
 #include "defs.h"
 #include "globals.c"
 
-int elf_symbol_index;
+int elf_symbol_index = 0;
 
 void elf_write_str(strbuf_t *elf_array, const char *vals)
 {

src/globals.c

@@ -18,8 +18,8 @@ char *intern_string(char *str);
 
 /* Lexer */
 char token_str[MAX_TOKEN_LEN];
-token_t next_token;
-char next_char;
+token_t next_token = 0;
+char next_char = 0;
 bool skip_newline = true;
 
 /* Token memory management */
@@ -32,7 +32,7 @@ bool preproc_match;
 /* Point to the first character after where the macro has been called. It is
  * needed when returning from the macro body.
  */
-int macro_return_idx;
+int macro_return_idx = 0;
 
 /* Global objects */
 
@@ -1236,6 +1236,10 @@ void strbuf_free(strbuf_t *src)
  */
 void global_init(void)
 {
+    FUNC_LIST.head = NULL;
+    FUNC_LIST.tail = NULL;
+    memset(REGS, 0, sizeof(regfile_t) * REG_CNT);
+
     MACROS_MAP = hashmap_create(MAX_ALIASES);
 
     /* Initialize arenas first so we can use them for allocation */