Make functions and variables exported by the IPA be extern "C"

Functions and variables that are exported by the IPA DSO (that
GDBserver needs to look up) should have "C" mangling, thus be declared
with extern "C".

Function and variable declarations need the extern "C" marker, but
variable definitions can't be marked extern, so the patch splits
IP_AGENT_EXPORT into three.

Building in C++ mode revealed that a few variables were missing
IP_AGENT_EXPORT, thus the IPA has been broken when stripped, even in C
mode...  So this ends being a bug fix as well.

gdb/ChangeLog:
2015-02-27  Pedro Alves  <palves@redhat.com>

	* common/agent.h (IPA_SYM_EXPORTED_NAME): New.
	(IPA_SYM): Use it.
	* common/common-defs.h (EXTERN_C_PUSH, EXTERN_C_POP): New macros.

gdb/gdbserver/ChangeLog:
2015-02-27  Pedro Alves  <palves@redhat.com>

	* linux-amd64-ipa.c (gdb_agent_get_raw_reg): Use
	IP_AGENT_EXPORT_FUNC.
	* linux-i386-ipa.c (gdb_agent_get_raw_reg): Use
	IP_AGENT_EXPORT_FUNC.
	* tracepoint.c (ATTR_USED, ATTR_NOINLINE, ATTR_CONSTRUCTOR)
	(IP_AGENT_EXPORT): Delete.
	(gdb_tp_heap_buffer, gdb_jump_pad_buffer, gdb_jump_pad_buffer_end)
	(gdb_trampoline_buffer, gdb_trampoline_buffer_end)
	(gdb_trampoline_buffer_error, collecting, gdb_collect)
	(stop_tracing, flush_trace_buffer, about_to_request_buffer_space)
	(trace_buffer_is_full, stopping_tracepoint, expr_eval_result)
	(error_tracepoint, tracepoints, tracing, trace_buffer_ctrl)
	(trace_buffer_ctrl_curr, trace_buffer_lo, trace_buffer_hi)
	(traceframe_read_count, traceframe_write_count)
	(traceframes_created, trace_state_variables, get_raw_reg)
	(get_trace_state_variable_value, set_trace_state_variable_value)
	(ust_loaded, helper_thread_id, cmd_buf): Use
	IPA_SYM_EXPORTED_NAME.
	(stop_tracing, flush_trace_buffer): Use IP_AGENT_EXPORT_FUNC.
	(tracepoints) Use IP_AGENT_EXPORT_VAR.
	(stopping_tracepoint, trace_buffer_is_full, expr_eval_result): Use
	IP_AGENT_EXPORT_VAR and wrap in EXTERN_C_PUSH/EXTERN_C_POP.
	(last_tracepoint): Move into !IN_PROCESS_AGENT block.
	(error_tracepoint): Use IP_AGENT_EXPORT_VAR and wrap in
	EXTERN_C_PUSH/EXTERN_C_POP.
	(trace_state_variables): Use IP_AGENT_EXPORT_VAR.
	(trace_buffer_lo, trace_buffer_hi): Use IP_AGENT_EXPORT_VAR and
	wrap in EXTERN_C_PUSH/EXTERN_C_POP.
	(trace_buffer_ctrl, trace_buffer_ctrl_curr)
	(traceframe_write_count, traceframe_read_count)
	(traceframes_created, tracing): Use IP_AGENT_EXPORT_VAR.
	(about_to_request_buffer_space, get_trace_state_variable_value)
	(set_trace_state_variable_value): Use IP_AGENT_EXPORT_FUNC.
	(collecting): Use IP_AGENT_EXPORT_VAR and wrap in
	EXTERN_C_PUSH/EXTERN_C_POP.
	(gdb_collect): Use IP_AGENT_EXPORT_FUNC.
	(ust_loaded, cmd_buf): Use IP_AGENT_EXPORT_VAR.
	(helper_thread_id, gdb_agent_capability): Use IP_AGENT_EXPORT_VAR
	and wrap in EXTERN_C_PUSH/EXTERN_C_POP.
	(gdb_tp_heap_buffer, gdb_jump_pad_buffer, gdb_jump_pad_buffer_end)
	(gdb_trampoline_buffer, gdb_trampoline_buffer_end)
	(gdb_trampoline_buffer_error): Use IP_AGENT_EXPORT_VAR.
	* tracepoint.h (ATTR_USED, ATTR_NOINLINE, EXPORTED_SYMBOL):
	Define.
	(IP_AGENT_EXPORT_FUNC, IP_AGENT_EXPORT_VAR)
	(IP_AGENT_EXPORT_VAR_DECL): Define.
	(tracing): Declare.
	(gdb_agent_get_raw_reg): Declare.

1 files changed, 49 insertions, 1 deletions

diff --git a/gdb/gdbserver/tracepoint.h b/gdb/gdbserver/tracepoint.h
index 2adcd56..30d0b58 100644
--- a/gdb/gdbserver/tracepoint.h
+++ b/gdb/gdbserver/tracepoint.h
@@ -25,7 +25,50 @@
 
 void initialize_tracepoint (void);
 
-extern int tracing;
+#if defined(__GNUC__)
+# define ATTR_USED __attribute__((used))
+# define ATTR_NOINLINE __attribute__((noinline))
+#else
+# define ATTR_USED
+# define ATTR_NOINLINE
+#endif
+
+/* How to make symbol public/exported.  */
+
+#if defined _WIN32 || defined __CYGWIN__
+# define EXPORTED_SYMBOL __declspec (dllexport)
+#else
+# if __GNUC__ >= 4
+#  define EXPORTED_SYMBOL __attribute__ ((visibility ("default")))
+# else
+#  define EXPORTED_SYMBOL
+# endif
+#endif
+
+/* Use these to make sure the functions and variables the IPA needs to
+   export (symbols GDBserver needs to query GDB about) are visible and
+   have C linkage.
+
+   Tag exported functions with IP_AGENT_EXPORT_FUNC, tag the
+   definitions of exported variables with IP_AGENT_EXPORT_VAR, and
+   variable declarations with IP_AGENT_EXPORT_VAR_DECL.  Variables
+   must also be exported with C linkage.  As we can't both use extern
+   "C" and initialize a variable in the same statement, variables that
+   don't have a separate declaration must use
+   EXTERN_C_PUSH/EXTERN_C_POP around their definition.  */
+
+#ifdef IN_PROCESS_AGENT
+# define IP_AGENT_EXPORT_FUNC EXTERN_C EXPORTED_SYMBOL ATTR_NOINLINE ATTR_USED
+# define IP_AGENT_EXPORT_VAR EXPORTED_SYMBOL ATTR_USED
+# define IP_AGENT_EXPORT_VAR_DECL EXTERN_C EXPORTED_SYMBOL
+#else
+# define IP_AGENT_EXPORT_FUNC
+# define IP_AGENT_EXPORT_VAR
+# define IP_AGENT_EXPORT_VAR_DECL extern
+#endif
+
+IP_AGENT_EXPORT_VAR_DECL int tracing;
+
 extern int disconnected_tracing;
 
 void tracepoint_look_up_symbols (void);
@@ -120,6 +163,11 @@ int agent_mem_read_string (struct eval_agent_expr_context *ctx,
 			   CORE_ADDR from,
 			   ULONGEST len);
 
+/* The prototype the get_raw_reg function in the IPA.  Each arch's
+   bytecode compiler emits calls to this function.  */
+IP_AGENT_EXPORT_FUNC ULONGEST gdb_agent_get_raw_reg
+  (const unsigned char *raw_regs, int regnum);
+
 /* Returns the address of the get_raw_reg function in the IPA.  */
 CORE_ADDR get_raw_reg_func_addr (void);
 /* Returns the address of the get_trace_state_variable_value