Some gdb_exception{,error,quit} tweaks

- Explicitly include <string> for std::string.

- Use std::make_shared to construct gdb_exception::message instead of
  operator new, avoiding one heap allocation (2 instead of 3).  Add
  'const char *fmt, va_list ap' parameters to
  gdb_exception{,error,quit}'s ctors, and do the std::make_shared in
  the gdb_exception ctor.

- gdb_exception_error's constructor does not need to have an 'enum
  return_reason' parameter, since it is always RETURN_ERROR, by
  definition.

- Similarly, gdb_exception_quit's contructor does not need to have
  'enum return_reason'/'enum errors' parameters.

- In the gdb_exception_{quit,_error} ctors that take a gdb_exception
  as argument, assert that they're being passed a gdb_exception object
  of the right 'reason'.

gdb/ChangeLog:
2019-04-08  Pedro Alves  <palves@redhat.com>

	* common/common-exceptions.c (throw_exception): Don't create
	named object to throw; throw directly.
	(throw_it): Likewise.  Don't initialize gdb_exception::message
	here, with new; pass FMT and AP to the ctor instead.
	* common/common-exceptions.h: Include <string>.
	(gdb_exception::gdb_exception(enum return_reason, enum errors,
	const char *, va_list)): New ctor.  Use std::make_shared.
	(gdb_exception_error::gdb_exception_error(enum return_reason, enum
	errors)): Delete.
	(gdb_exception_error::gdb_exception_error(enum errors, const char
	*, va_list)): New.
	(gdb_exception_error::gdb_exception_error(const gdb_exception &)):
	Add assertion.
	(gdb_exception_quit::gdb_exception_quit(enum return_reason, enum
	errors)): Delete.
	(gdb_exception_quit::gdb_exception_quit(const char *, va_list)): New.
	(gdb_exception_quit::gdb_exception_quit(const gdb_exception &)):
	Add assertion.

gdb/ChangeLog

@@ -1,3 +1,24 @@
+2019-04-08  Pedro Alves  <palves@redhat.com>
+
+	* common/common-exceptions.c (throw_exception): Don't create
+	named object to throw; throw directly.
+	(throw_it): Likewise.  Don't initialize gdb_exception::message
+	here, with new; pass FMT and AP to the ctor instead.
+	* common/common-exceptions.h: Include <string>.
+	(gdb_exception::gdb_exception(enum return_reason, enum errors,
+	const char *, va_list)): New ctor.  Use std::make_shared.
+	(gdb_exception_error::gdb_exception_error(enum return_reason, enum
+	errors)): Delete.
+	(gdb_exception_error::gdb_exception_error(enum errors, const char
+	*, va_list)): New.
+	(gdb_exception_error::gdb_exception_error(const gdb_exception &)):
+	Add assertion.
+	(gdb_exception_quit::gdb_exception_quit(enum return_reason, enum
+	errors)): Delete.
+	(gdb_exception_quit::gdb_exception_quit(const char *, va_list)): New.
+	(gdb_exception_quit::gdb_exception_quit(const gdb_exception &)):
+	Add assertion.
+
 2019-04-08  Tom Tromey  <tom@tromey.com>
 
 	* valops.c (value_rtti_indirect_type): Replace throw_exception

gdb/common/common-exceptions.c

@@ -184,15 +184,9 @@ void
 throw_exception (const gdb_exception &exception)
 {
   if (exception.reason == RETURN_QUIT)
-    {
-      gdb_exception_quit ex (exception);
-      throw ex;
-    }
+    throw gdb_exception_quit (exception);
   else if (exception.reason == RETURN_ERROR)
-    {
-      gdb_exception_error ex (exception);
-      throw ex;
-    }
+    throw gdb_exception_error (exception);
   else
     gdb_assert_not_reached ("invalid return reason");
 }
@@ -202,17 +196,9 @@ throw_it (enum return_reason reason, enum errors error, const char *fmt,
 	  va_list ap)
 {
   if (reason == RETURN_QUIT)
-    {
-      gdb_exception_quit ex (reason, error);
-      ex.message.reset (new std::string (string_vprintf (fmt, ap)));
-      throw ex;
-    }
+    throw gdb_exception_quit (fmt, ap);
   else if (reason == RETURN_ERROR)
-    {
-      gdb_exception_error ex (reason, error);
-      ex.message.reset (new std::string (string_vprintf (fmt, ap)));
-      throw ex;
-    }
+    throw gdb_exception_error (error, fmt, ap);
   else
     gdb_assert_not_reached ("invalid return reason");
 }

gdb/common/common-exceptions.h

@@ -23,6 +23,7 @@
 #include <setjmp.h>
 #include <new>
 #include <memory>
+#include <string>
 
 /* Reasons for calling throw_exceptions().  NOTE: all reason values
    must be different from zero.  enum value 0 is reserved for internal
@@ -123,6 +124,15 @@ struct gdb_exception
   {
   }
 
+  gdb_exception (enum return_reason r, enum errors e,
+		 const char *fmt, va_list ap)
+    ATTRIBUTE_PRINTF (4, 0)
+    : reason (r),
+      error (e),
+      message (std::make_shared<std::string> (string_vprintf (fmt, ap)))
+  {
+  }
+
   /* The copy constructor exists so that we can mark it "noexcept",
      which is a good practice for any sort of exception object.  */
   gdb_exception (const gdb_exception &other) noexcept
@@ -214,27 +224,31 @@ extern int exceptions_state_mc_catch (struct gdb_exception *, int);
 
 struct gdb_exception_error : public gdb_exception
 {
-  gdb_exception_error (enum return_reason r, enum errors e)
-    : gdb_exception (r, e)
+  gdb_exception_error (enum errors e, const char *fmt, va_list ap)
+    ATTRIBUTE_PRINTF (3, 0)
+    : gdb_exception (RETURN_ERROR, e, fmt, ap)
   {
   }
 
   explicit gdb_exception_error (const gdb_exception &ex) noexcept
     : gdb_exception (ex)
   {
+    gdb_assert (ex.reason == RETURN_ERROR);
   }
 };
 
 struct gdb_exception_quit : public gdb_exception
 {
-  gdb_exception_quit (enum return_reason r, enum errors e)
-    : gdb_exception (r, e)
+  gdb_exception_quit (const char *fmt, va_list ap)
+    ATTRIBUTE_PRINTF (2, 0)
+    : gdb_exception (RETURN_QUIT, GDB_NO_ERROR, fmt, ap)
   {
   }
 
   explicit gdb_exception_quit (const gdb_exception &ex) noexcept
     : gdb_exception (ex)
   {
+    gdb_assert (ex.reason == RETURN_QUIT);
   }
 };