Add -fpic and -fPIC options

chibicc.h

@@ -440,5 +440,6 @@ void hashmap_test(void);
 bool file_exists(char *path);
 
 extern StringArray include_paths;
+extern bool opt_fpic;
 extern bool opt_fcommon;
 extern char *base_file;

codegen.c

@@ -73,6 +73,21 @@ static void gen_addr(Node *node) {
       return;
     }
 
+    if (opt_fpic) {
+      // Thread-local variable
+      if (node->var->is_tls) {
+        println("  data16 lea %s@tlsgd(%%rip), %%rdi", node->var->name);
+        println("  .value 0x6666");
+        println("  rex64");
+        println("  call __tls_get_addr@PLT");
+        return;
+      }
+
+      // Function or global variable
+      println("  mov %s@GOTPCREL(%%rip), %%rax", node->var->name);
+      return;
+    }
+
     // Thread-local variable
     if (node->var->is_tls) {
       println("  mov %%fs:0, %%rax");

main.c

@@ -6,6 +6,7 @@ typedef enum {
 
 StringArray include_paths;
 bool opt_fcommon = true;
+bool opt_fpic;
 
 static FileType opt_x;
 static StringArray opt_include;
@@ -256,6 +257,11 @@ static void parse_args(int argc, char **argv) {
       continue;
     }
 
+    if (!strcmp(argv[i], "-fpic") || !strcmp(argv[i], "-fPIC")) {
+      opt_fpic = true;
+      continue;
+    }
+
     if (!strcmp(argv[i], "-cc1-input")) {
       base_file = argv[++i];
       continue;

test/driver.sh

@@ -259,4 +259,10 @@ $chibicc -c -MD -MF $tmp/md-mf.d -I. $tmp/md2.c
 grep -q -z '^md2.o:.*md2\.c .*/out2\.h' $tmp/md-mf.d
 check -MD
 
+echo 'extern int bar; int foo() { return bar; }' | $chibicc -fPIC -xc -c -o $tmp/foo.o -
+cc -shared -o $tmp/foo.so $tmp/foo.o
+echo 'int foo(); int bar=3; int main() { foo(); }' > $tmp/main.c
+$chibicc -o $tmp/foo $tmp/main.c $tmp/foo.so
+check -fPIC
+
 echo OK