https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68450

            Bug ID: 68450
           Summary: regex matching different from ECMAScript?
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lcoquelle at gmail dot com
  Target Milestone: ---

Created attachment 36777
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36777&action=edit
Code sample

Using a complex regex to remove comment in JSON file (...), the behaviour seems
to differ from ECMAScript.
FYI: boost::regex 1.59 seems to have the correct behaviour.

Regex: ((['"])(?:(?!\2|\\).|\\.)*\2)|\/\/[^\n]*|\/\*(?:[^*]|\*(?!\/))*\*\/
(can be try here: https://regex101.com/r/vI2iW5/2#javascript)

Input string: "Entry": "Value", // Skip "me"
Expected output: "Entry": "Value", 
Real output: "Entry": "Value", // Skip "me"



Attached a code sample.
Compiling output as below:


> /usr/local/gcc49/bin/g++ -v -save-temps -Wall -std=gnu++14 re.cc 
Using built-in specs.
COLLECT_GCC=/usr/local/gcc49/bin/g++
COLLECT_LTO_WRAPPER=/usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /usr/local/src/gcc-4.9.2/configure --disable-multilib
--enable-cloog-backend=isl --enable-gold=default --enable-languages=c,c++
--enable-lto --enable-libssp --enable-plugins --enable-plugin
--with-build-config=bootstrap-lto --enable-stage1-checking=release
--prefix=/usr/local/gcc49
Thread model: posix
gcc version 4.9.2 (GCC) 
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-std=gnu++1y' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
 /usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/cc1plus -E -quiet
-v -D_GNU_SOURCE re.cc -mtune=generic -march=x86-64 -std=gnu++1y -Wall
-fpch-preprocess -o re.ii
ignoring nonexistent directory
"/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../include/c++/4.9.2

/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../include/c++/4.9.2/x86_64-unknown-linux-gnu

/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../include/c++/4.9.2/backward
 /usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/include
 /usr/local/include
 /usr/local/gcc49/include
 /usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/include-fixed
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-std=gnu++1y' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
 /usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/cc1plus
-fpreprocessed re.ii -quiet -dumpbase re.cc -mtune=generic -march=x86-64
-auxbase re -Wall -std=gnu++1y -version -o re.s
GNU C++ (GCC) version 4.9.2 (x86_64-unknown-linux-gnu)
        compiled by GNU C version 4.9.2, GMP version 6.0.0, MPFR version 3.1.2,
MPC version 1.0.2
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C++ (GCC) version 4.9.2 (x86_64-unknown-linux-gnu)
        compiled by GNU C version 4.9.2, GMP version 6.0.0, MPFR version 3.1.2,
MPC version 1.0.2
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 4c9e457b752b2d9171dda4de0a18535a
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-std=gnu++1y' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'

/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../x86_64-unknown-linux-gnu/bin/as
-v --64 -o re.o re.s
GNU assembler version 2.24 (x86_64-unknown-linux-gnu) using BFD version (GNU
Binutils) 2.24
COMPILER_PATH=/usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/:/usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/:/usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/:/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/:/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/:/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../x86_64-unknown-linux-gnu/bin/
LIBRARY_PATH=/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/:/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../x86_64-unknown-linux-gnu/lib/:/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-std=gnu++1y' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
 /usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/collect2 -plugin
/usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/liblto_plugin.so
-plugin-opt=/usr/local/gcc49/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/lto-wrapper
-plugin-opt=-fresolution=re.res -plugin-opt=-pass-through=-lgcc_s
-plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lgcc
--eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2
/lib/../lib64/crt1.o /lib/../lib64/crti.o
/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/crtbegin.o
-L/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2
-L/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../lib64
-L/lib/../lib64 -L/usr/lib/../lib64
-L/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../../../x86_64-unknown-linux-gnu/lib
-L/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/../../.. re.o
-lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc
/usr/local/gcc49/lib/gcc/x86_64-unknown-linux-gnu/4.9.2/crtend.o
/lib/../lib64/crtn.o


Running output:

> ./a.out 
"Field": "Value"  
"Field": "Value"  // Skip "me"

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