[Bug c++/77263] New: comment /* */ is ignored in some cases

[bremende55 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77263

            Bug ID: 77263
           Summary: comment /* */ is ignored in some cases
           Product: gcc
           Version: 6.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bremende55 at gmail dot com
  Target Milestone: ---

The following code compiles and gives the correct result:
#include <iostream>
#include <regex>
#include <string>

int main() {
  std::string astring("// x /*  meaningless comment start  ");
  // /*
  std::string result = std::regex_replace(
                    astring, std::regex("//[^\n]*/\\*"),  "ZZ ");
  std::cout << "result = " << result << '\n';
  // expected: ZZ   meaningless comment start
  // */
  std::cout << "astring = " << astring << '\n';
}

BUT when I comment out the lines in the middle, i.e. 
#include <iostream>
#include <regex>
#include <string>

int main() {
  std::string astring("// x /*  meaningless comment start  ");
  /*
  std::string result = std::regex_replace(
                    astring, std::regex("//[^\n]*/\\*"),  "ZZ ");
  std::cout << "result = " << result << '\n';
  // expected: ZZ   meaningless comment start
  */
  std::cout << "astring = " << astring << '\n';
}

the compile detects errors in the out-commented code.
g++ -v 
yields:
Es werden eingebaute Spezifikationen verwendet.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/local/lib/gcc/x86_64-pc-linux-gnu/6.1.0/lto-wrapper
Ziel: x86_64-pc-linux-gnu
Konfiguriert mit: ../gcc-6.1.0/configure --enable-languages=c,c++
Thread-Modell: posix
gcc-Version 6.1.0 (GCC)