[build] Address symbol visibility and DSO builds

Added an `API` macro in `j6/api.h` that expands to mark the given
declaration as a default-visible symbol. Also change `format` and
`vformat` to non-template functions, and make calls to `main`, `exit`,
and the library init functions in `_start` GOT-relative.

src/libraries/j6/include/j6/channel.hh

@@ -8,10 +8,11 @@
 
 #include <stddef.h>
 #include <j6/types.h>
+#include <util/api.h>
 
 namespace j6 {
 
-class channel
+class API channel
 {
 public:
     /// Create a new channel of the given size.

src/libraries/j6/include/j6/init.h

@@ -4,6 +4,7 @@
 
 #include <stdint.h>
 #include <j6/types.h>
+#include <util/api.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -71,7 +72,7 @@ struct j6_init_args
 
 
 /// Find the first handle of the given type held by this process
-j6_handle_t j6_find_first_handle(j6_object_type obj_type);
+j6_handle_t API j6_find_first_handle(j6_object_type obj_type);
 
 /// Get the init args
 const j6_init_args * j6_get_init_args();

src/libraries/j6/include/j6/memutils.h

@@ -2,6 +2,7 @@
 /// \file memutils.h
 /// Standard mem*() library functions
 
+#include <util/api.h>
 #include <__j6libc/restrict.h>
 #include <__j6libc/size_t.h>
 
@@ -9,9 +10,9 @@
 extern "C" {
 #endif
 
-void *memcpy(void * restrict s1, const void * restrict s2, size_t n);
-void *memmove(void * restrict s1, const void * restrict s2, size_t n);
-void *memset(void *s, int c, size_t n);
+void * API memcpy(void * restrict s1, const void * restrict s2, size_t n);
+void * API memmove(void * restrict s1, const void * restrict s2, size_t n);
+void * API memset(void *s, int c, size_t n);
 
 #ifdef __cplusplus
 } // extern "C"

src/libraries/j6/include/j6/protocols/service_locator.hh

@@ -1,9 +1,10 @@
 #include <j6/protocols/service_locator.h>
 #include <j6/types.h>
+#include <util/api.h>
 
 namespace j6::proto::sl {
 
-class client
+class API client
 {
 public:
     /// Constructor.

src/libraries/j6/include/j6/protocols/vfs.hh

@@ -1,9 +1,14 @@
+#pragma once
+/// \file vfs.hh
+/// C++ client interface for VFS protocol
+
 #include <j6/protocols/vfs.h>
 #include <j6/types.h>
+#include <util/api.h>
 
 namespace j6::proto::vfs {
 
-class client
+class API client
 {
 public:
     /// Constructor.

src/libraries/j6/include/j6/sysconf.h.cog

@@ -10,6 +10,7 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <util/api.h>
 
 /*[[[cog code generation
 from os.path import join
@@ -35,7 +36,7 @@ enum j6_sysconf_arg
 
 /// Get the kernel configuration value specified by
 /// the argument.
-unsigned long j6_sysconf(j6_sysconf_arg arg);
+unsigned long API j6_sysconf(j6_sysconf_arg arg);
 
 #ifdef __cplusplus
 } // extern C

src/libraries/j6/include/j6/syslog.hh

@@ -2,13 +2,15 @@
 /// \file j6/syslog.hh
 /// Utility function for writing messages to the kernel log
 
+#include <util/api.h>
+
 // The kernel depends on libj6 for some shared code,
 // but should not include the user-specific code.
 #ifndef __j6kernel
 
 namespace j6 {
 
-void syslog(const char *fmt, ...);
+void API syslog(const char *fmt, ...);
 
 } // namespace j6
 

src/libraries/j6/init.cpp

@@ -36,13 +36,13 @@ j6_find_first_handle(j6_object_type obj_type)
     return j6_handle_invalid;
 }
 
-const j6_init_args *
+const j6_init_args * API
 j6_get_init_args()
 {
     return &init_args;
 }
 
-extern "C" void
+extern "C" void API
 __init_libj6(uint64_t arg0, uint64_t arg1)
 {
     init_args.args[0] = arg0;

src/libraries/j6/syslog.cpp

@@ -4,6 +4,7 @@
 
 #include <util/format.h>
 #include <j6/syscalls.h>
+#include <j6/syslog.hh>
 
 namespace j6 {
 

src/libraries/libc/arch/amd64/crt/crt0.s

@@ -12,17 +12,17 @@ _libc_crt0_start:
     push 0
     mov rbp, rsp
 
-    call __init_libj6
+    call __init_libj6 wrt ..got
     mov rbx, rax
 
-    call __init_libc
+    call __init_libc wrt ..got
 
     mov rdi, 0
     mov rsi, rsp
     mov rdx, 0    ; TODO: actually parse stack for argc, argv, envp
     mov rcx, rbx
-    call main
+    call main wrt ..got
 
     mov rdi, rax
-    call exit
+    call exit wrt ..got
 .end:

src/libraries/libc/libc.module

@@ -27,7 +27,7 @@ for ext in ("h",):
 libc = module("libc",
     kind = "lib",
     deps = [ "j6" ],
-    output = "libc.a",
+    basename = "libc",
     include_phase = "late",
     sources = sources,
     public_headers = headers,
@@ -35,6 +35,7 @@ libc = module("libc",
 
 libc.variables["ccflags"] = [
     "${ccflags}",
+    "-fvisibility=default",
     "-DPRINTF_SUPPORT_DECIMAL_SPECIFIERS=0",
     "-DPRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS=0",
 ]

src/libraries/util/format.cpp

@@ -88,7 +88,6 @@ append_string(char_t *&out, size_t &count, size_t max, unsigned width, char_t co
     }
 }
 
-} // namespace
 
 template <typename char_t> size_t
 vformat(counted<char_t> output, char_t const *format, va_list va)
@@ -169,20 +168,28 @@ vformat(counted<char_t> output, char_t const *format, va_list va)
     return count;
 }
 
-template <typename char_t> size_t
-format(counted<char_t> output, const char_t *format, ...)
+} // namespace
+
+size_t API format(counted<char> output, const char *format, ...)
 {
     va_list va;
     va_start(va, format);
-    size_t result = vformat<char_t>(output, format, va);
+    size_t result = vformat<char>(output, format, va);
     va_end(va);
     return result;
 }
 
-template size_t format<char>(counted<char> output, const char *format, ...);
-template size_t vformat<char>(counted<char> output, const char *format, va_list va);
+size_t API format(counted<wchar_t> output, const wchar_t *format, ...)
+{
+    va_list va;
+    va_start(va, format);
+    size_t result = vformat<wchar_t>(output, format, va);
+    va_end(va);
+    return result;
+}
+
+size_t API vformat(counted<char> output, const char *format, va_list va) { return vformat<char>(output, format, va); }
+size_t API vformat(counted<wchar_t> output, const wchar_t *format, va_list va) { return vformat<wchar_t>(output, format, va); }
 
-template size_t format<wchar_t>(counted<wchar_t> output, const wchar_t *format, ...);
-template size_t vformat<wchar_t>(counted<wchar_t> output, const wchar_t *format, va_list va);
 
 } //namespace util

src/libraries/util/include/util/allocator.h

@@ -2,6 +2,9 @@
 /// \file allocator.h
 /// Definition of the allocator interface.
 
+#include <stddef.h>
+#include <j6/memutils.h>
+
 namespace util {
 
 // Allocators are types with three static methods with these signatures

src/libraries/util/include/util/api.h

@@ -0,0 +1,7 @@
+#pragma once
+/// \file api.h
+/// Library interface visibility macros
+
+#ifndef API
+#define API __attribute__ ((visibility ("default")))
+#endif

src/libraries/util/include/util/bip_buffer.h

@@ -6,11 +6,12 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include <util/api.h>
 #include <util/spinlock.h>
 
 namespace util {
 
-class bip_buffer
+class API bip_buffer
 {
 public:
     /// Default constructor. Creates a zero-size buffer.

src/libraries/util/include/util/format.h

@@ -4,14 +4,16 @@
 #pragma once
 
 #include <stdarg.h>
+#include <util/api.h>
 #include <util/counted.h>
 
 namespace util {
 
-template <typename char_t>
-size_t format(counted<char_t> output, const char_t *format, ...);
+size_t API format(counted<char> output, const char *format, ...);
+size_t API vformat(counted<char> output, const char *format, va_list va);
 
-template <typename char_t>
-size_t vformat(counted<char_t> output, const char_t *format, va_list va);
+
+size_t API format(counted<wchar_t> output, const wchar_t *format, ...);
+size_t API vformat(counted<wchar_t> output, const wchar_t *format, va_list va);
 
 }

src/libraries/util/include/util/spinlock.h

@@ -3,6 +3,7 @@
 #pragma once
 
 #include <stdint.h>
+#include <util/api.h>
 
 #ifdef __j6kernel
 extern "C" uint32_t __current_thread_id();
@@ -11,7 +12,7 @@ extern "C" uint32_t __current_thread_id();
 namespace util {
 
 /// An MCS based spinlock
-class spinlock
+class API spinlock
 {
 public:
     spinlock();

src/libraries/util/util.module

@@ -10,6 +10,7 @@ module("util",
     ],
     public_headers = [
         "util/allocator.h",
+        "util/api.h",
         "util/assert.h",
         "util/basic_types.h",
         "util/bip_buffer.h",