[Bug c++/58824] New: Lambda trigger internal compiler error

["thomas.sanchz at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58824

            Bug ID: 58824
           Summary: Lambda trigger internal compiler error
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: thomas.sanchz at gmail dot com

Created attachment 31058
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31058&action=edit
Source file + ii + s

Hi,

Please see in attached file the source triggering an internal error in gcc.

The source file is compiled like this:

$> g++ -std=c++11 -W -Wall -Wextra test.cpp 
test.cpp: In instantiation of ‘struct test<dummy>::__lambda0’:
test.cpp:5:8:   required from here
test.cpp:8:20: internal compiler error: in tsubst_copy, at cp/pt.c:12116
         { "test", [this]{} }

The bug is triggered when `this` is captured from a template class and the
lambda is assigned directly from the class definition.

The platform tested is an ubuntu 13.10 with default shipped compiler:

$gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.8.1-10ubuntu8' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.8 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --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-4.8-amd64/jre
--enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-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 --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 4.8.1 (Ubuntu/Linaro 4.8.1-10ubuntu8) 

The bug is still present in gcc4.9 (tested via: http://gcc.godbolt.org/).
I joined the *i files even if I doubt that they'll be helpful in this
particular bug.
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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/58742] [4.7/4.8/4.9 Regression] pointer arithmetic simplification
Date: Mon, 21 Oct 2013 09:24:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idX742

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |middle-end
      Known to work|                            |4.1.2
   Target Milestone|---                         |4.7.4
            Summary|pointer arithmetic          |[4.7/4.8/4.9 Regression]
                   |simplification              |pointer arithmetic
                   |                            |simplification
      Known to fail|                            |4.2.0

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
This case is a signed exact division followed by an unsigned multiply.  We do
that to avoid introducing undefined signed overflow.

signed exact division and unsigned multiply still cancel out though, handling
of these is in extract_muldiv (ugh).  I'm not going to enhance that but
pattern match this case.  Testing

Index: gcc/fold-const.c
==================================================================--- gcc/fold-const.c    (revision 203885)
+++ gcc/fold-const.c    (working copy)
@@ -11002,6 +11002,13 @@ fold_binary_loc (location_t loc,
                                fold_build2_loc (loc, MULT_EXPR, type,
                                             build_int_cst (type, 2) , arg1));

+         /* ((T) (X /[ex] C)) * C cancels out if the conversion is
+            sign-changing only.  */
+         if (TREE_CODE (arg1) == INTEGER_CST
+             && TREE_CODE (arg0) == EXACT_DIV_EXPR
+             && operand_equal_p (arg1, TREE_OPERAND (arg0, 1), 0))
+           return fold_convert_loc (loc, type, TREE_OPERAND (arg0, 0));
+
          strict_overflow_p = false;
          if (TREE_CODE (arg1) == INTEGER_CST
              && 0 != (tem = extract_muldiv (op0, arg1, code, NULL_TREE,

note that this simplification worked in 4.1.2 but stopped working in 4.2.0.
Likely a wrong-code fix for extract_muldiv disabled this case (the way
that function works makes special casing a pattern like above impossible).