cc: detect -lunwind for C (already automatic for C++) and build libun…

…wind when needed

src/build_sysroot.c

@@ -1031,13 +1031,19 @@ err_t build_sysroot(const compiler_t* c, int flags) {
     finalize_build_component(c, lockfd, &err, "librt");
   }
 
+  if (!err && (flags & SYSROOT_BUILD_UNWIND) &&
+      target_has_syslib(&c->target, SYSLIB_UNWIND) &&
+      build_component(c, &lockfd, &err, flags, "libunwind"))
+  {
+    err = build_libunwind(c);
+    finalize_build_component(c, lockfd, &err, "libunwind");
+  }
+
   if (!err && (flags & SYSROOT_BUILD_CXX) &&
       target_has_syslib(&c->target, SYSLIB_CXX) &&
       build_component(c, &lockfd, &err, flags, "libcxx"))
   {
-    assert(target_has_syslib(&c->target, SYSLIB_UNWIND));
     assert(target_has_syslib(&c->target, SYSLIB_CXXABI));
-    err = build_libunwind(c);
     if (!err) err = build_cxx_config_site(c); // __config_site header
     if (!err) err = build_libcxxabi(c);
     if (!err) err = build_libcxx(c);
@@ -1136,7 +1142,7 @@ static bool build_sysroot_for_target(compiler_t* compiler, const target_t* targe
     log("building sysroot for %s", tmpbuf);
   }
 
-  int flags = SYSROOT_BUILD_CXX;
+  int flags = SYSROOT_BUILD_CXX | SYSROOT_BUILD_UNWIND;
   if (opt_force) flags |= SYSROOT_BUILD_FORCE;
   if (( err = build_sysroot(compiler, flags) )) {
     dlog("build_sysroot: %s", err_str(err));

src/cc.c

@@ -76,6 +76,7 @@ int cc_main(int user_argc, char* user_argv[], bool iscxx) {
   bool link_libc = true;
   bool link_libcxx = iscxx;
   bool link_librt = true;
+  bool explicit_link_libunwind = false; // -lunwind
   bool startfiles = true;
   bool nostdinc = false;
   bool custom_ld = false;
@@ -185,7 +186,15 @@ int cc_main(int user_argc, char* user_argv[], bool iscxx) {
         iscompiling = true;
       } else if (streq(arg, "-x")) {
         iscompiling = true;
+      } else if (string_startswith(arg, "-L") || string_startswith(arg, "-l")) {
+        if (streq(arg+2, "unwind"))
+          explicit_link_libunwind = true;
+        has_link_flags = true;
       } else if (streq(arg, "-L") || streq(arg, "-l")) {
+        if (i+1 < user_argc) {
+          if (streq(user_argv[i+1], "unwind"))
+            explicit_link_libunwind = true;
+        }
         has_link_flags = true;
       } else if (streq(arg, "-o")) {
         // infer "no linking" based on output filename
@@ -347,6 +356,8 @@ int cc_main(int user_argc, char* user_argv[], bool iscxx) {
   // build sysroot
   if (!custom_sysroot && !print_only) {
     int sysroot_build_flags = 0;
+    if (explicit_link_libunwind || link_libcxx)
+      sysroot_build_flags |= SYSROOT_BUILD_UNWIND;
     if (link_libcxx)
       sysroot_build_flags |= SYSROOT_BUILD_CXX;
     if (( err = build_sysroot(&c, sysroot_build_flags) ))
@@ -401,6 +412,9 @@ int cc_main(int user_argc, char* user_argv[], bool iscxx) {
     }
   }
 
+  if (explicit_link_libunwind)
+    strlist_addf(&args, "-isystem%s/libunwind/include", coroot);
+
   // linker flags
   if (link) {
 

src/compiler.h

@@ -416,8 +416,9 @@ void scope_iterate(scope_t* s, u32 maxdepth, scopeit_t it, void* nullable ctx);
 const char* visibility_str(nodeflag_t flags);
 
 // sysroot
-#define SYSROOT_BUILD_CXX   (1<<0) // enable libc++, libc++abi, libunwind
-#define SYSROOT_BUILD_FORCE (1<<1) // (re)build even if up to date
+#define SYSROOT_BUILD_FORCE  (1<<0) // (re)build even if up to date
+#define SYSROOT_BUILD_CXX    (1<<1) // enable libc++, libc++abi
+#define SYSROOT_BUILD_UNWIND (1<<2) // enable libunwind
 err_t build_sysroot(const compiler_t* c, int flags); // build_sysroot.c
 const char* syslib_filename(const target_t* target, syslib_t);