From f7c6f42310233479ea6339430b7c1ca1f9ec68e1 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Wed, 30 May 2018 14:18:47 +0100 Subject: [PATCH] Mark END_CATCH as ATTRIBUTE_NORETURN (-Wmaybe-uninitialized warnings) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This commit fixes a set of -Wmaybe-uninitialized warnings in GDB and GDBserver, seen with GCC 7.3.1 on F27 at -O2. Specifically, all of these: src/gdb/breakpoint.c:5040:4: warning: ‘e’ may be used uninitialized in this function [-Wmaybe-uninitialized] src/gdb/cli/cli-cmds.c:277:71: warning: ‘tracker’ may be used uninitialized in this function [-Wmaybe-uninitialized] src/gdb/cli/cli-cmds.c:302:22: warning: ‘word’ may be used uninitialized in this function [-Wmaybe-uninitialized] src/gdb/gdbserver/server.c:1895:7: warning: ‘result’ may be used uninitialized in this function [-Wmaybe-uninitialized] src/gdb/gdbserver/server.c:1966:7: warning: ‘result’ may be used uninitialized in this function [-Wmaybe-uninitialized] For example, looking at one of the gdbserver ones in more detail: ../../../src/gdb/gdbserver/server.c: In function ‘int handle_qxfer_btrace_conf(const char*, gdb_byte*, const gdb_byte*, ULONGEST, LONGEST)’: ../../../src/gdb/gdbserver/server.c:1966:7: warning: ‘result’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (result != 0) ^~ In this case (like the others), the 'result' variable is assigned in both TRY and CATCH blocks: TRY { result = target_read_btrace_conf (thread->btrace, &cache); if (result != 0) memcpy (own_buf, cache.buffer, cache.used_size); } CATCH (exception, RETURN_MASK_ERROR) { sprintf (own_buf, "E.%s", exception.message); result = -1; } END_CATCH if (result != 0) return -3; so it would seem like the warning is bogus. However, END_CATCH is really a catch block in disguise, and that path indeed does not initialize the variable: #define END_CATCH \ catch (...) \ { \ exception_rethrow (); \ } \ } exception_rethrow does not return normally (it rethrows the current exception after running cleanups), but the compiler can not see that. If it could return normally, then indeed 'result' could be used uninitialized if the TRY block threw some non-gdb exception, which would be caught by END_CATCH. The fix it to let the compiler know that the exception_rethrow does not return normally, using ATTRIBUTE_NORETURN. gdb/ChangeLog: 2018-05-30 Pedro Alves * common/common-exceptions.h (exception_rethrow): Use ATTRIBUTE_NORETURN. --- gdb/ChangeLog | 5 +++++ gdb/common/common-exceptions.h | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 0a730c88f94..c38ff5b14a4 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2018-05-30 Pedro Alves + + * common/common-exceptions.h (exception_rethrow): Use + ATTRIBUTE_NORETURN. + 2018-05-29 Simon Marchi * breakpoint.c (print_solib_event, check_status_catch_solib): diff --git a/gdb/common/common-exceptions.h b/gdb/common/common-exceptions.h index 15c85e28ab5..e873f9d0615 100644 --- a/gdb/common/common-exceptions.h +++ b/gdb/common/common-exceptions.h @@ -146,7 +146,7 @@ extern int exceptions_state_mc_catch (struct gdb_exception *, int); #if GDB_XCPT != GDB_XCPT_SJMP extern void *exception_try_scope_entry (void); extern void exception_try_scope_exit (void *saved_state); -extern void exception_rethrow (void); +extern void exception_rethrow (void) ATTRIBUTE_NORETURN; #endif /* Macro to wrap up standard try/catch behavior.