factor dlerror and error-setting code out of dynlink.c

the ultimate goal of this change is to get all code used in libc.a out
of dynlink.c, so that the dynamic linker code can be moved to its own
tree and object files in the src tree can all be shared between libc.a
and libc.so.

src/ldso/dlerror.c

+#include <dlfcn.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include "pthread_impl.h"
+
+char *dlerror()
+{
+	pthread_t self = __pthread_self();
+	if (!self->dlerror_flag) return 0;
+	self->dlerror_flag = 0;
+	char *s = self->dlerror_buf;
+	if (s == (void *)-1)
+		return "Dynamic linker failed to allocate memory for error message";
+	else
+		return s;
+}
+
+void __dl_thread_cleanup(void)
+{
+	pthread_t self = __pthread_self();
+	if (self->dlerror_buf != (void *)-1)
+		free(self->dlerror_buf);
+}
+
+__attribute__((__visibility__("hidden")))
+void __dl_vseterr(const char *fmt, va_list ap)
+{
+	va_list ap2;
+	va_copy(ap2, ap);
+	pthread_t self = __pthread_self();
+	if (self->dlerror_buf != (void *)-1)
+		free(self->dlerror_buf);
+	size_t len = vsnprintf(0, 0, fmt, ap2);
+	va_end(ap2);
+	char *buf = malloc(len+1);
+	if (buf) {
+		vsnprintf(buf, len+1, fmt, ap);
+	} else {
+		buf = (void *)-1;	
+	}
+	self->dlerror_buf = buf;
+	self->dlerror_flag = 1;
+}
+
+__attribute__((__visibility__("hidden")))
+void __dl_seterr(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	__dl_vseterr(fmt, ap);
+	va_end(ap);
+}

src/ldso/dynlink.c

@@ -1945,29 +1945,13 @@ int __dlinfo(void *dso, int req, void *res)
 	return 0;
 }
 
-char *dlerror()
-{
-	pthread_t self = __pthread_self();
-	if (!self->dlerror_flag) return 0;
-	self->dlerror_flag = 0;
-	char *s = self->dlerror_buf;
-	if (s == (void *)-1)
-		return "Dynamic linker failed to allocate memory for error message";
-	else
-		return s;
-}
-
 int dlclose(void *p)
 {
 	return invalid_dso_handle(p);
 }
 
-void __dl_thread_cleanup(void)
-{
-	pthread_t self = __pthread_self();
-	if (self->dlerror_buf != (void *)-1)
-		free(self->dlerror_buf);
-}
+__attribute__((__visibility__("hidden")))
+void __dl_vseterr(const char *, va_list);
 
 static void error(const char *fmt, ...)
 {
@@ -1982,19 +1966,6 @@ static void error(const char *fmt, ...)
 		return;
 	}
 #endif
-	pthread_t self = __pthread_self();
-	if (self->dlerror_buf != (void *)-1)
-		free(self->dlerror_buf);
-	size_t len = vsnprintf(0, 0, fmt, ap);
+	__dl_vseterr(fmt, ap);
 	va_end(ap);
-	char *buf = malloc(len+1);
-	if (buf) {
-		va_start(ap, fmt);
-		vsnprintf(buf, len+1, fmt, ap);
-		va_end(ap);
-	} else {
-		buf = (void *)-1;	
-	}
-	self->dlerror_buf = buf;
-	self->dlerror_flag = 1;
 }