From 0df0cce7c63c064e086deda7384a7dd82fefe228 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Sat, 24 Apr 2021 19:26:04 -0400 Subject: gdbsupport: allow passing format string to scoped_debug_start_end A little thing that bothers me with scoped_debug_start_end is that it's not possible to pass a format string to add context to the messages: the start and end messages are fixed. It was done like this at the time because there's the risk that debug output is not enabled on entry (when the constructor runs) but is enabled on exit (when the destructor runs). For example, a user debugging from a top-gdb may manually enable a debug_foo variable. If debug output is disabled while the constructor runs, we won't render the format string (to minimize overhead) so it won't be available in the destructor. I think it would be nice to be able to use a format string along with scoped_debug_start_end, and I think it's unfortunate that such a narrow use case prevents it. So with this patch, I propose that we allow passing a format string to scoped_debug_start_end, and if the rare situation described above happens, then we just show a "sorry, message not available" kind of message. The following patch makes use of this. gdbsupport/ChangeLog: * common-debug.h (struct scoped_debug_start_end) : Change start_msg/end_msg for start_prefix/end_prefix. Add format string parameter and make variadic. <~scoped_debug_start_end>: Adjust. : Rename to... : ... this. : New. : New. (scoped_debug_start_end): Make variadic. (scoped_debug_enter_exit): Adjust. Change-Id: I9427ce8877a246a46694b3a1fec3837dc6954d6e --- gdbsupport/ChangeLog | 14 ++++++++++ gdbsupport/common-debug.h | 66 ++++++++++++++++++++++++++++++++++++++--------- 2 files changed, 68 insertions(+), 12 deletions(-) (limited to 'gdbsupport') diff --git a/gdbsupport/ChangeLog b/gdbsupport/ChangeLog index 0f3de6d..83416cf 100644 --- a/gdbsupport/ChangeLog +++ b/gdbsupport/ChangeLog @@ -1,5 +1,19 @@ 2021-04-24 Simon Marchi + * common-debug.h (struct scoped_debug_start_end) + : Change start_msg/end_msg for + start_prefix/end_prefix. Add format string parameter and make + variadic. + <~scoped_debug_start_end>: Adjust. + : Rename to... + : ... this. + : New. + : New. + (scoped_debug_start_end): Make variadic. + (scoped_debug_enter_exit): Adjust. + +2021-04-24 Simon Marchi + * observable.h (class observable) : Add name parameter. : New field. diff --git a/gdbsupport/common-debug.h b/gdbsupport/common-debug.h index 7288b69..8b9b004 100644 --- a/gdbsupport/common-debug.h +++ b/gdbsupport/common-debug.h @@ -20,8 +20,11 @@ #ifndef COMMON_COMMON_DEBUG_H #define COMMON_COMMON_DEBUG_H +#include "gdbsupport/gdb_optional.h" #include "gdbsupport/preprocessor.h" +#include + /* Set to true to enable debugging of hardware breakpoint/ watchpoint support code. */ @@ -94,20 +97,39 @@ struct scoped_debug_start_end MODULE and FUNC are forwarded to debug_prefixed_printf. - START_MSG and END_MSG are the statements to print on construction and - destruction, respectively. */ + START_PREFIX and END_PREFIX are the statements to print on construction and + destruction, respectively. + + If the FMT format string is non-nullptr, then a `: ` is appended to the + messages, followed by the rendering of that format string. The format + string is rendered during construction and is re-used as is for the + message on exit. */ scoped_debug_start_end (bool &debug_enabled, const char *module, - const char *func, const char *start_msg, - const char *end_msg) + const char *func, const char *start_prefix, + const char *end_prefix, const char *fmt, ...) + ATTRIBUTE_NULL_PRINTF (7, 8) : m_debug_enabled (debug_enabled), m_module (module), m_func (func), - m_end_msg (end_msg) + m_end_prefix (end_prefix), + m_with_format (fmt != nullptr) { if (m_debug_enabled) { - debug_prefixed_printf (m_module, m_func, "%s", start_msg); + if (fmt != nullptr) + { + va_list args; + va_start (args, fmt); + m_msg = string_vprintf (fmt, args); + va_end (args); + + debug_prefixed_printf (m_module, m_func, "%s: %s", + start_prefix, m_msg->c_str ()); + } + else + debug_prefixed_printf (m_module, m_func, "%s", start_prefix); + ++debug_print_depth; m_must_decrement_print_depth = true; } @@ -125,7 +147,22 @@ struct scoped_debug_start_end if (m_debug_enabled) { - debug_prefixed_printf (m_module, m_func, "%s", m_end_msg); + if (m_with_format) + { + if (m_msg.has_value ()) + debug_prefixed_printf (m_module, m_func, "%s: %s", + m_end_prefix, m_msg->c_str ()); + else + { + /* A format string was passed to the constructor, but debug + control variable wasn't set at the time, so we don't have the + rendering of the format string. */ + debug_prefixed_printf (m_module, m_func, "%s: <%s debugging was not enabled on entry>", + m_end_prefix, m_module); + } + } + else + debug_prefixed_printf (m_module, m_func, "%s", m_end_prefix); } } @@ -133,20 +170,25 @@ private: bool &m_debug_enabled; const char *m_module; const char *m_func; - const char *m_end_msg; + const char *m_end_prefix; + + /* The result of formatting the format string in the constructor. */ + gdb::optional m_msg; + + /* True is a non-nullptr format was passed to the constructor. */ + bool m_with_format; /* This is used to handle the case where debugging is enabled during construction but not during destruction, or vice-versa. We want to make sure there are as many increments are there are decrements. */ - bool m_must_decrement_print_depth = false; }; /* Helper to define a module-specific start/end debug macro. */ -#define scoped_debug_start_end(debug_enabled, module, msg) \ +#define scoped_debug_start_end(debug_enabled, module, fmt, ...) \ scoped_debug_start_end CONCAT(scoped_debug_start_end, __LINE__) \ - (debug_enabled, module, __func__, "start: " msg, "end: " msg) + (debug_enabled, module, __func__, "start", "end", fmt, ##__VA_ARGS__) /* Helper to define a module-specific enter/exit debug macro. This is a special case of `scoped_debug_start_end` where the start and end messages are "enter" @@ -154,6 +196,6 @@ private: #define scoped_debug_enter_exit(debug_enabled, module) \ scoped_debug_start_end CONCAT(scoped_debug_start_end, __LINE__) \ - (debug_enabled, module, __func__, "enter", "exit") + (debug_enabled, module, __func__, "enter", "exit", nullptr) #endif /* COMMON_COMMON_DEBUG_H */ -- cgit v1.1