From: Alex Bennée <alex.bennee@linaro.org>
Date: Thu, 6 Mar 2025 16:16:31 +0000 (+0000)
Subject: meson.build: default to -gsplit-dwarf for debug info
X-Git-Tag: v10.0.0-rc0~19^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=563b1a35ed1f1151505d4fe5f723827d1b3fd4bc;p=thirdparty%2Fqemu.git

meson.build: default to -gsplit-dwarf for debug info

This option is supported by both gcc (since 4.7) and clang (since
7.0). Not only does this make the linkers job easier by reducing the
amount of ELF it needs to parse it also reduces the total build size
quite considerably. In my case a default build went from 5.8G to
3.9G (vs 1.9G for --disable-debug-info).

The --disable-split-debug option allows distros to keep all the info
together for ease of packaging.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Link: https://lore.kernel.org/r/20250306161631.2477685-1-alex.bennee@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/meson.build b/meson.build
index 6da4eb317c..4899d896de 100644
--- a/meson.build
+++ b/meson.build
@@ -601,6 +601,10 @@ if get_option('tsan')
   qemu_ldflags = ['-fsanitize=thread'] + qemu_ldflags
 endif
 
+if get_option('debug') and get_option('split_debug')
+  qemu_cflags += '-gsplit-dwarf'
+endif
+
 # Detect support for PT_GNU_RELRO + DT_BIND_NOW.
 # The combination is known as "full relro", because .got.plt is read-only too.
 qemu_ldflags += cc.get_supported_link_arguments('-Wl,-z,relro', '-Wl,-z,now')
@@ -4583,6 +4587,8 @@ if have_rust
   summary_info += {'bindgen':         bindgen.full_path()}
   summary_info += {'bindgen version': bindgen.version()}
 endif
+# option_cflags is purely for the summary display, meson will pass
+# -g/-O options directly
 option_cflags = (get_option('debug') ? ['-g'] : [])
 if get_option('optimization') != 'plain'
   option_cflags += ['-O' + get_option('optimization')]
diff --git a/meson_options.txt b/meson_options.txt
index 59d973bca0..3432123fee 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -362,6 +362,8 @@ option('debug_mutex', type: 'boolean', value: false,
        description: 'mutex debugging support')
 option('debug_stack_usage', type: 'boolean', value: false,
        description: 'measure coroutine stack usage')
+option('split_debug', type: 'boolean', value: true,
+       description: 'split debug info from object files')
 option('qom_cast_debug', type: 'boolean', value: true,
        description: 'cast debugging support')
 option('slirp_smbd', type : 'feature', value : 'auto',
diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
index 3e8e00852b..aca6e68830 100644
--- a/scripts/meson-buildoptions.sh
+++ b/scripts/meson-buildoptions.sh
@@ -504,6 +504,8 @@ _meson_option_parse() {
     --disable-strict-rust-lints) printf "%s" -Dstrict_rust_lints=false ;;
     --enable-strip) printf "%s" -Dstrip=true ;;
     --disable-strip) printf "%s" -Dstrip=false ;;
+    --enable-split-debug) printf "%s" -Dsplit_debug=true ;;
+    --disable-split-debug) printf "%s" -Dsplit_debug=false ;;
     --sysconfdir=*) quote_sh "-Dsysconfdir=$2" ;;
     --enable-tcg) printf "%s" -Dtcg=enabled ;;
     --disable-tcg) printf "%s" -Dtcg=disabled ;;