[Bug c++/78523] New: ICE on valid lambda code with implicit capture

[rjpcal at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78523

            Bug ID: 78523
           Summary: ICE on valid lambda code with implicit capture
           Product: gcc
           Version: 5.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rjpcal at gmail dot com
  Target Milestone: ---

Created attachment 40146
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40146&action=edit
Short snippet (8 lines) yielding the ICE

$ cat test.cc
int bar();

void foo()
{
  const int t = bar();
  auto f = [=](auto x){ return t; };
  f(0);
}

$ g++ -std=gnu++14 -c test.cc
test.cc: In lambda function:
test.cc:6:35: internal compiler error: Segmentation fault
   auto f = [=](auto x){ return t; };
                                   ^

Results with different capture lists:

[=] -- ICE (shown above)
[&] -- also ICE
[t] -- works as expected (no ICE)


$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
5.4.0-6ubuntu1~16.04.4' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-5 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib
--disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 


I see Bug 49598 has a very similar-sounding summary and test case but that was
apparently found+fixed in 4.6/4.7, and this is occurring in 5.4.