From 4e5de36a36452ef9fe29ac55f7812f2bb9005d95 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Fri, 9 Oct 2020 15:09:17 +0900
Subject: [PATCH] Add -shared option

---
 main.c         | 25 +++++++++++++++++++++----
 test/driver.sh |  6 ++++++
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/main.c b/main.c
index 694c11a..414a08f 100644
--- a/main.c
+++ b/main.c
@@ -20,6 +20,7 @@ static bool opt_c;
 static bool opt_cc1;
 static bool opt_hash_hash_hash;
 static bool opt_static;
+static bool opt_shared;
 static char *opt_MF;
 static char *opt_MT;
 static char *opt_o;
@@ -284,6 +285,12 @@ static void parse_args(int argc, char **argv) {
       continue;
     }
 
+    if (!strcmp(argv[i], "-shared")) {
+      opt_shared = true;
+      strarray_push(&ld_extra_args, "-shared");
+      continue;
+    }
+
     if (!strcmp(argv[i], "-hashmap-test")) {
       hashmap_test();
       exit(0);
@@ -598,9 +605,15 @@ static void run_linker(StringArray *inputs, char *output) {
   char *libpath = find_libpath();
   char *gcc_libpath = find_gcc_libpath();
 
-  strarray_push(&arr, format("%s/crt1.o", libpath));
-  strarray_push(&arr, format("%s/crti.o", libpath));
-  strarray_push(&arr, format("%s/crtbegin.o", gcc_libpath));
+  if (opt_shared) {
+    strarray_push(&arr, format("%s/crti.o", libpath));
+    strarray_push(&arr, format("%s/crtbeginS.o", gcc_libpath));
+  } else {
+    strarray_push(&arr, format("%s/crt1.o", libpath));
+    strarray_push(&arr, format("%s/crti.o", libpath));
+    strarray_push(&arr, format("%s/crtbegin.o", gcc_libpath));
+  }
+
   strarray_push(&arr, format("-L%s", gcc_libpath));
   strarray_push(&arr, "-L/usr/lib/x86_64-linux-gnu");
   strarray_push(&arr, "-L/usr/lib64");
@@ -636,7 +649,11 @@ static void run_linker(StringArray *inputs, char *output) {
     strarray_push(&arr, "--no-as-needed");
   }
 
-  strarray_push(&arr, format("%s/crtend.o", gcc_libpath));
+  if (opt_shared)
+    strarray_push(&arr, format("%s/crtendS.o", gcc_libpath));
+  else
+    strarray_push(&arr, format("%s/crtend.o", gcc_libpath));
+
   strarray_push(&arr, format("%s/crtn.o", libpath));
   strarray_push(&arr, NULL);
 
diff --git a/test/driver.sh b/test/driver.sh
index e6d5bf9..37c295b 100755
--- a/test/driver.sh
+++ b/test/driver.sh
@@ -282,4 +282,10 @@ check -static
 file $tmp/foo | grep -q 'statically linked'
 check -static
 
+# -shared
+echo 'extern int bar; int foo() { return bar; }' > $tmp/foo.c
+echo 'int foo(); int bar=3; int main() { foo(); }' > $tmp/bar.c
+$chibicc -fPIC -shared -o $tmp/foo.so $tmp/foo.c $tmp/bar.c
+check -shared
+
 echo OK