[PATCH 0/1] gold: Suppress "unused" variable warning on Clang

[PATCH 0/1] gold: Suppress "unused" variable warning on Clang

[Tsukasa OI]

Hello,

[Background]

When we build Binutils and GDB with Clang, it causes a build failure due to
warnings generated by Clang and the default -Werror configuration.

I MOSTLY managed to make ALL ARCHITECTURE ENABLED Binutils and GDB
-Werror-free on Clang 15.0.0 (note that this does not necessarily mean
warning-free) and this patchset is a part of it (GNU gold).

-   It still requires -Wno-implicit-function-declaration
    on the LatticeMicro32 and M32R simulators.  Except them, all Binutils /
    GDB components can be built with Clang by default with my tree.

Full Clang 15.0.0 -Werror-free branch in development is available at:
<https://github.com/a4lg/binutils-gdb/tree/clang-nowarn-dev>

Tested configuration:
-   Ubuntu 22.04.1 LTS (x86_64)
-   LLVM / Clang 15.0.0 (built from source)
-   Configuration examples:
    $srcdir/configure \
        --enable-targets=all \
        --enable-multilib --enable-ld --enable-gold --enable-nls \
        CC=clang CXX=clang++ CCLD=clang CXXLD=clang++ \
        CFLAGS='  -O2 -g -Wno-implicit-function-declaration' \
        CXXFLAGS='-O2 -g -Wno-implicit-function-declaration'
    $srcdir/configure \
        --target=riscv64-unknown-linux-gnu \
        --enable-multilib --enable-ld --enable-gold --enable-nls \
        CC=clang CXX=clang++ CCLD=clang CXXLD=clang++ \
        CFLAGS='-O2 -g' CXXFLAGS='-O2 -g'


[About this Patch]

Clang generates a warning if there is a variable that is set but not used
otherwise ("-Wunused-but-set-variable").  On the default configuration, it
causes a build failure (unless "--disable-werror" is specified).

Because the cause of this error is in the Bison-generated code
($(binutils)/gold/yyscript.y -> $(srcdir)/gold/yyscript.c),
this commit suppresses this warning ("-Wunused-but-set-variable") by placing
DIAGNOSTIC_IGNORE_UNUSED_BUT_SET_VARIABLE macro at the end of user
prologue on yyscript.y.


Thanks,
Tsukasa




Tsukasa OI (1):
  gold: Suppress "unused" variable warning on Clang

 gold/yyscript.y | 3 +++
 1 file changed, 3 insertions(+)


base-commit: c21736aed1d4877e090df60362413669dbdc391d
-- 
2.34.1

[PATCH 1/1] gold: Suppress "unused" variable warning on Clang

[Tsukasa OI]

Clang generates a warning if there is a variable that is set but not used
otherwise ("-Wunused-but-set-variable").  On the default configuration, it
causes a build failure (unless "--disable-werror" is specified).

Because the cause of this error is in the Bison-generated code
($(srcdir)/gold/yyscript.y -> $(builddir)/gold/yyscript.c),
this commit suppresses this warning ("-Wunused-but-set-variable") by placing
DIAGNOSTIC_IGNORE_UNUSED_BUT_SET_VARIABLE macro at the end of user
prologue on yyscript.y.

gold/ChangeLog:

	* yyscript.y: Suppress -Wunused-but-set-variable warning on
	the Bison-generated code.
---
 gold/yyscript.y | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gold/yyscript.y b/gold/yyscript.y
index 909786f0ddd..fe8f6812712 100644
--- a/gold/yyscript.y
+++ b/gold/yyscript.y
@@ -26,6 +26,7 @@
 %{
 
 #include "config.h"
+#include "diagnostics.h"
 
 #include <stddef.h>
 #include <stdint.h>
@@ -34,6 +35,8 @@
 
 #include "script-c.h"
 
+DIAGNOSTIC_IGNORE_UNUSED_BUT_SET_VARIABLE
+
 %}
 
 /* We need to use a pure parser because we might be multi-threaded.
-- 
2.34.1

Re: [PATCH 1/1] gold: Suppress "unused" variable warning on Clang

[Alan Modra]

On Mon, Sep 26, 2022 at 10:35:40AM +0000, Tsukasa OI via Binutils wrote:
> 	* yyscript.y: Suppress -Wunused-but-set-variable warning on
> 	the Bison-generated code.

Applied, thanks.

-- 
Alan Modra
Australia Development Lab, IBM