From 5a99adb86018c10da294e7556544e401c492c2fb Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Thu, 30 Jul 2020 09:23:01 +0200 Subject: [PATCH] [gdb/build] Fix Wmaybe-uninitialized in gdb/ui-style.h When building CFLAGS/CXXFLAGS="-O2 -g -Wall" and gcc 4.8.5, we run into: ... src/gdb/cli/cli-style.c:154:42: warning: '*((void*)& +8)' \ may be used uninitialized in this function [-Wmaybe-uninitialized] src/gdb/cli/cli-style.c:154:42: warning: '*((void*)& +9)' \ may be used uninitialized in this function [-Wmaybe-uninitialized] src/gdb/cli/cli-style.c:154:42: warning: '*((void*)& +10)' \ may be used uninitialized in this function [-Wmaybe-uninitialized] ... The root cause is that the data members of class color, nested in struct ui_file_style in gdb/ui-style.h: ... bool m_simple; int m_value; uint8_t m_red, m_green, m_blue; ... are only partially initialized by this constructor: ... color (int c) : m_simple (true), m_value (c) { gdb_assert (c >= -1 && c <= 255); } ... but the default copy constructor will copy all the fields. The member m_simple acts as a discriminant, to indicate which other members are valid: - m_value (with m_simple == true) - m_red, m_green, m_blue (with m_simple == false) So, we don't need storage for both m_value and m_red/m_green/m_blue at the same time. Fix this by wrapping the respective members in a union: ... bool m_simple; union { int m_value; struct { uint8_t m_red, m_green, m_blue; }; }; ... which also fixes the warning. Build and reg-tested on x86_64-linux. gdb/ChangeLog: 2020-07-30 Tom de Vries PR build/26320 * ui-style.h (struct ui_file_style::color): Wrap m_value and m_red/m_green/m_blue in a union. --- gdb/ChangeLog | 6 ++++++ gdb/ui-style.h | 10 ++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 4d4d62e302a..a61a57355b5 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2020-07-30 Tom de Vries + + PR build/26320 + * ui-style.h (struct ui_file_style::color): Wrap m_value and + m_red/m_green/m_blue in a union. + 2020-07-29 Tom de Vries PR tdep/26280 diff --git a/gdb/ui-style.h b/gdb/ui-style.h index 48ab52d5ea9..9cb6dda5fcb 100644 --- a/gdb/ui-style.h +++ b/gdb/ui-style.h @@ -126,8 +126,14 @@ struct ui_file_style private: bool m_simple; - int m_value; - uint8_t m_red, m_green, m_blue; + union + { + int m_value; + struct + { + uint8_t m_red, m_green, m_blue; + }; + }; }; /* Intensity settings that are available. */ -- 2.30.2