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From: "alex.miller at gmx dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug lto/100010] New: ICE in lto_output_node, at lto-cgraph.c:447
 (-fdevirtualize-at-ltrans)
Date: Sat, 10 Apr 2021 01:36:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100010

            Bug ID: 100010
           Summary: ICE in lto_output_node, at lto-cgraph.c:447
                    (-fdevirtualize-at-ltrans)
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alex.miller at gmx dot de
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

Building lcdf-typetools-2.108 fails with an ICE while linking the mmafm tool
(with gcc-10 using the flags "-O3 -flto -fdevirtualize-at-ltrans").

Here's a reduced sample that reproduces the issue (even with -O2):
---
struct String {
        String(char);
        ~String();
};
struct ErrorHandler {
        virtual String decorate(const String &);
};
String ErrorHandler::decorate(const String &str) {
        decorate(str);
        return 0;
}
struct LandmarkErrorHandler : ErrorHandler {
        String _landmark;
        LandmarkErrorHandler();
        String decorate(const String &);
};
String LandmarkErrorHandler::decorate(const String &) {
        return ErrorHandler::decorate(0);
}
struct Charstring {
        virtual ~Charstring();
        virtual void process() =3D 0;
} *interpret_cs;
Charstring::~Charstring() {}
struct : Charstring {
        void process() {}
} _cdv;
int main() {
        LandmarkErrorHandler();
        interpret_cs->process();
}
---

$ g++ -O2 -flto -fdevirtualize-at-ltrans a.cc
during IPA pass: static-var
lto1: internal compiler error: in lto_output_node, at lto-cgraph.c:447
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://bugs.gentoo.org/> for instructions.
lto-wrapper: fatal error: g++ returned 1 exit status
compilation terminated.
/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../x86_64-pc-linux-gnu/bin=
/ld:
error: lto-wrapper failed
collect2: error: ld returned 1 exit status

Reducing the sources seems a bit brittle, like often with LTO:
* Combining all sources in a single file changed the error message to
  "lto1: internal compiler error: Segmentation fault", but minimizing made
  the error location reappear. The result is very similar to a multi-file
  reduction.
* Reduced sample fails with -O2, full sources need -O3.
* With g++-9.3.0 the reduced sample doesn't trigger the ICE, but the origin=
al
  sources do (at lto-cgraph.c:453).
Let me know if you need another sample.=