[ruby-core:72852] [Ruby trunk - Bug #11979] gcc-6 fails to optimize regcomp.c:compile_length_quantifier_node()

Issue #11979 has been updated by Takeshi Nishimatsu.

Subject changed from gcc-6 fails to optimize regcomp.c to gcc-6 fails to optimize regcomp.c:compile_length_quantifier_node()

gcc-6 fails to optimize ruby-2.3.0/regcomp.c:compile_length_quantifier_node()
and cannot build the ruby. Even the -O1 optimization option fails.
Adding `__attribute__((optimize("O0")))` before the function can evade this issue.
I confirmed this issue both on GNU/Linux and Mac OS X.

Please note that there are two compile_length_quantifier_node() in ruby-2.3.0/regcomp.c.
gcc-6 fails to optimize second one at the line 985.

gcc-4.9.2 could build ruby-2.3.0.
/usr/bin/gcc of Mac OS X (Apple LLVM version 7.0.2 (clang-700.1.81)) could
build ruby-2.3.0, too.

I will report this issue to https://gcc.gnu.org/bugzilla/ tomorrow.

~~~
$ wget https://cache.ruby-lang.org/pub/ruby/2.3/ruby-2.3.0.tar.xz
$ shasum ruby-2.3.0.tar.xz | grep 96e620e38af351c8da63e40cfe217ec79f912ba1
$ tar xf ruby-2.3.0.tar.xz
$ mkdir  ruby-2.3.0/build_on_MacOSX
$ cd     ruby-2.3.0/build_on_MacOSX
$ /usr/local/bin/gcc --version
gcc (GCC) 6.0.0 20151115 (experimental)
$ ../configure CC=/usr/local/bin/gcc
$ make -j4
    :
generating encdb.h
../template/encdb.h.tmpl:63:in `block (4 levels) in <main>': x_emoji.h:8: ENC_REPLICATE: UTF-8 is not defined yet. (replica UTF8-DoCoMo) (ArgumentError)
    :
$ sed -e '984 a\
> __attribute__((optimize("O0")))' ../regcomp.c > regcomp.c
$ diff -u ../regcomp.c .
--- ../regcomp.c        2015-12-09 16:30:44.000000000 +0900
+++ ./regcomp.c 2016-01-14 08:21:52.798816125 +0900
@@ -982,6 +982,7 @@
 #else /* USE_COMBINATION_EXPLOSION_CHECK */
 static int
+__attribute__((optimize("O0")))
 compile_length_quantifier_node(QtfrNode* qn, regex_t* reg)
 {
   int len, mod_tlen;
$ make V=1 encdb.h
    :
./miniruby -I../lib -I. -I.ext/common  ../tool/generic_erb.rb -c -o encdb.h ../template/encdb.h.tmpl ../enc enc
encdb.h updated
$ make -j4
$ make check
    :
# Running tests:

Finished tests in 453.556568s, 34.7388 tests/s, 4931.0101 assertions/s.
15756 tests, 2236492 assertions, 0 failures, 0 errors, 53 skips

ruby -v: ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin15]
check succeeded
$
~~~


----------------------------------------
Bug #11979: gcc-6 fails to optimize regcomp.c:compile_length_quantifier_node()
https://bugs.ruby-lang.org/issues/11979#change-56087

* Author: Takeshi Nishimatsu
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 2.2.4, 2.3.0
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
----------------------------------------
This may be a GCC version specific issue.
gcc-6, an experimental snapshot from http://ftp.tsukuba.wide.ad.jp/software/gcc/snapshots/6-20160110/ ,
fails to compile ruby-2.2.4 and ruby-2.3.0 with an error of
**template/encdb.h.tmpl:63:in `block (4 levels) in <main>': x_emoji.h:8: ENC_REPLICATE: UTF-8 is not defined yet. (replica UTF8-DoCoMo) (ArgumentError)** .
I confirmed it both on Linux and Mac OS X.

gcc-4.9.2 could compile ruby-2.3.0.
/usr/bin/gcc of Mac OS X (Apple LLVM version 7.0.2 (clang-700.1.81)) could compile ruby-2.3.0, too.

Maybe, I should report it to https://gcc.gnu.org/bugzilla/ .
Could you tell me how to make small reproducible code?
(Or, please report it to the bugzilla with small code ;-)

Compile log:

~~~
$ uname -a
Linux emerald01 2.6.32-573.12.1.el6.x86_64 #1 SMP Tue Dec 15 21:19:08 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
$ tar xf ruby-2.3.0.tar.xz
$ mkdir ruby-2.3.0/Linux-x86_64-gcc-6-20160110-emerald01
$ cd    ruby-2.3.0/Linux-x86_64-gcc-6-20160110-emerald01
$ pwd
$ ../configure
$ make -j16
$ make
$ make V=1
	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
	XCFLAGS = -D_FORTIFY_SOURCE=2 -fstack-protector -fno-strict-overflow -fvisibility=hidden -DRUBY_EXPORT -fPIE
	CPPFLAGS =   -I. -I.ext/include/x86_64-linux -I../include -I..
	DLDFLAGS = -fstack-protector -pie
	SOLIBS = -lgmp
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --enable-languages=c,c++,fortran,go,objc --with-gmp-include=/usr/local/include --with-gmp-lib=/usr/local/lib64 --with-mpfr-include=/usr/local/include --with-mpfr-lib=/usr/local/lib64 --with-mpc-include=/usr/local/include --with-mpc-lib=/usr/local/lib64
Thread model: posix
gcc version 6.0.0 20160110 (experimental) (GCC)
./miniruby -I../lib -I. -I.ext/common  ../enc/make_encmake.rb --builtin-encs="enc/ascii.o enc/us_ascii.o enc/unicode.o enc/utf_8.o" --builtin-transes="enc/trans/newline.o" --module  enc.mk
./miniruby -I../lib -I. -I.ext/common  ../tool/generic_erb.rb -c -o encdb.h ../template/encdb.h.tmpl ../enc enc
../template/encdb.h.tmpl:63:in `block (4 levels) in <main>': x_emoji.h:8: ENC_REPLICATE: UTF-8 is not defined yet. (replica UTF8-DoCoMo) (ArgumentError)
	from ../template/encdb.h.tmpl:43:in `each_line'
	from ../template/encdb.h.tmpl:43:in `block (3 levels) in <main>'
	from ../template/encdb.h.tmpl:41:in `open'
	from ../template/encdb.h.tmpl:41:in `block (2 levels) in <main>'
	from ../template/encdb.h.tmpl:38:in `each'
	from ../template/encdb.h.tmpl:38:in `block in <main>'
	from ../template/encdb.h.tmpl:34:in `each'
	from ../template/encdb.h.tmpl:34:in `<main>'
	from /home002/t-nissie/COMMON/work/ruby/ruby/ruby-2.3.0/lib/erb.rb:864:in `eval'
	from /home002/t-nissie/COMMON/work/ruby/ruby/ruby-2.3.0/lib/erb.rb:864:in `result'
	from ../tool/generic_erb.rb:38:in `<main>'
make: *** [encdb.h] Error 1
~~~



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