Bug #10710: can't compile ruby 2.2.0 with gcc versions older than 4.4.0

• Status: Closed
• Assignee: nobu (Nobuyoshi Nakada)
• Target version: -
• ruby -v: 2.2.0
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

[drkaes (Stefan Kaes)]

compilation stops because gcc before 4.4.0 does not support the flag -Wno-packed-bitfield-compat.

patch can be found here: https://github.com/skaes/rvm-patchsets/blob/master/patches/ruby/2.2.0/railsexpress/05-fix-packed-bitfield-compat-warning-for-older-gccs.patch

[drkaes (Stefan Kaes)]

• File 05-fix-packed-bitfield-compat-warning-for-older-gccs.patch 05-fix-packed-bitfield-compat-warning-for-older-gccs.patch added

[normalperson (Eric Wong)]

[e-mail] wrote:

compilation stops because gcc before 4.4.0 does not support the flag
-Wno-packed-bitfield-compat.

I'm curious what error you saw. An ancient CentOS 5.4 x86-64 machine
managed to build it using: gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-46)

--- a/configure.in
+++ b/configure.in
@@ -788,6 +788,9 @@ rb_cv_warnflags="$warnflags"
 if test "$GCC:${warnflags+set}:no" = yes::no; then
     if test $gcc_major -ge 4; then
 	extra_warning=-Werror=extra-tokens
+        if test $gcc_major -gt 4 -o $gcc_minor -ge 4; then
+            extra_warning="$extra_warning -Wno-packed-bitfield-compat"
+        fi

I think "||" is preferable to "-o" for portability. But maybe not a
problem nowadays...

[drkaes (Stefan Kaes)]

$ gcc --version
gcc (Debian 4.3.2-1.1) 4.3.2

The compilation of a given source file fails as soon as the compiler needs to emit some warning:

gcc -Wno-packed-bitfield-compat some_warning.c
some_warning.c: In function ‘main’:
some_warning.c:3: warning: return type of ‘main’ is not ‘int’
At top level:
cc1: error: unrecognized command line option "-Wno-packed-bitfield-compat"

[normalperson (Eric Wong)]

The compilation of a given source file fails as soon as the compiler
needs to emit some warning:

Right, but ./configure detects that failure, disables the
-Wno-packed-bitfield-compat switch, and the rest of the build continues
without it, right?

[drkaes (Stefan Kaes)]

no. it aborts the build.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Feedback

Could you show your config.log file, around checking -Wno-packed-bitfield-compat?

[drkaes (Stefan Kaes)]

the problem is that the compiler accepts the warning flag but fails to compile a piece of code as soon as it tries to emit some warning.

configure:7495: checking whether -Wno-packed-bitfield-compat is accepted as CFLAGS
configure:7518: gcc -c -g -O2  -Wno-packed-bitfield-compat  conftest.c >&5
configure:7518: $? = 0
configure:7533: result: yes

[drkaes (Stefan Kaes)]

here's the build output:

~/src/ruby-2.2.0 $ make
	CC = gcc
	LD = ld
	LDSHARED = gcc -shared
	CFLAGS = -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat -std=iso9899:1999  -fPIC 
	XCFLAGS = -D_FORTIFY_SOURCE=2 -fstack-protector -fno-strict-overflow -fvisibility=hidden -DRUBY_EXPORT
	CPPFLAGS =   -I. -I.ext/include/x86_64-linux -I./include -I.
	DLDFLAGS = -Wl,-soname,libruby.so.2.2  -fstack-protector  
	SOLIBS = -lpthread -lrt -lgmp -ldl -lcrypt -lm  
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.2-1.1' --with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3 --program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr --enable-cld --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.3.2 (Debian 4.3.2-1.1) 
compiling main.c
compiling dmydln.c
compiling miniinit.c
compiling miniprelude.c
copying dummy probes.h
compiling array.c
compiling bignum.c
bignum.c: In function ‘rb_absint_numwords’:
bignum.c:3370: warning: ‘nlz_bits’ may be used uninitialized in this function
At top level:
cc1: error: unrecognized command line option "-Wno-packed-bitfield-compat"
make: *** [bignum.o] Error 1

[drkaes (Stefan Kaes)]

• Status changed from Feedback to Closed

no longer relevant