rtld: Clang fixes

1) Fix clang warnings
2) Fix r_debug_state function

The r_debug_state function is a hook required for gdb.  Clang will inline
the function, but because it is empty, it won't generate any calls to it.
This results in gdb backtraces being corrupted.  Fixed with the following
hack obtained from FreeBSD SVN 225366.

Fix it by marking the function __noinline, and inserting an empty asm
statement that pretends to clobber memory.  This forces the compiler to
emit calls to the r_debug_state() function throughout rtld.c

diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index c17fe49..5cd1dff 100644 (file)
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -147,7 +147,7 @@ static void ld_utrace_log(int, void *, void *, size_t, int, const char *);
 static void rtld_fill_dl_phdr_info(const Obj_Entry *obj,
     struct dl_phdr_info *phdr_info);
 
-void r_debug_state(struct r_debug *, struct link_map *);
+void r_debug_state(struct r_debug *, struct link_map *) __noinline;
 
 /*
  * Data declarations.
@@ -1024,8 +1024,8 @@ digest_dynamic(Obj_Entry *obj, int early)
                    obj->textrel = true;
                if (dynp->d_un.d_val & DF_BIND_NOW)
                    obj->bind_now = true;
-               if (dynp->d_un.d_val & DF_STATIC_TLS)
-                   ;
+               /*if (dynp->d_un.d_val & DF_STATIC_TLS)
+                   ;*/
            break;
 
        case DT_FLAGS_1:
@@ -1033,8 +1033,8 @@ digest_dynamic(Obj_Entry *obj, int early)
                    obj->z_noopen = true;
                if ((dynp->d_un.d_val & DF_1_ORIGIN) && trust)
                    obj->z_origin = true;
-               if (dynp->d_un.d_val & DF_1_GLOBAL)
-                       /* XXX */;
+               /*if (dynp->d_un.d_val & DF_1_GLOBAL)
+                   XXX ;*/
                if (dynp->d_un.d_val & DF_1_BIND_NOW)
                    obj->bind_now = true;
                if (dynp->d_un.d_val & DF_1_NODELETE)
@@ -2724,6 +2724,14 @@ linkmap_delete(Obj_Entry *obj)
 void
 r_debug_state(struct r_debug* rd, struct link_map *m)
 {
+    /*
+     * The following is a hack to force the compiler to emit calls to
+     * this function, even when optimizing.  If the function is empty,
+     * the compiler is not obliged to emit any code for calls to it,
+     * even when marked __noinline.  However, gdb depends on those
+     * calls being made.
+     */
+    __asm __volatile("" : : : "memory");
 }
 
 /*