[Debian-lego-team] Bug#1121607: gcc-h8300-hms: fails to compile some C++ file, internal error

[Matthew Sheets]

Issues stemming from GCC 15 seem to be surfacing elsewhere, too.

Consider the packages overview for the Debian LEGO team.
 * https://qa.debian.org/developer.php?email=debian-lego-team%40lists.alioth.debian.org

Package gcc-h8300-hms shows Buildd failing on sh4.

Taking a closer look at that, and it was okay until comparatively recently:
 * https://buildd.debian.org/status/logs.php?pkg=gcc-h8300-hms&arch=sh4

Log from the last "successful" build on 2025-04-10:
 * https://buildd.debian.org/status/fetch.php?pkg=gcc-h8300-hms&arch=sh4&ver=1%3A3.4.6%2Bdfsg2-7&stamp=1744322988&raw=0

Log from the next subsequent failed build on 2025-09-07:
 * https://buildd.debian.org/status/fetch.php?pkg=gcc-h8300-hms&arch=sh4&ver=1%3A3.4.6%2Bdfsg2-8&stamp=1757254675&raw=0


In each of those logs, scroll down to the "Build environment" section and note
a key difference in the "Toolchain package versions" listed for each:
 * Succeeding 2024-04-10 build:  GCC 14
 * Failing 2025-09-07 build:  GCC 15

Furthermore, the error given for the 2025-09-07 build failure is an
Internal Compiler Error:
```
qemu: uncaught target signal 11 (Segmentation fault) - core dumped
gcc: internal compiler error: Segmentation fault signal terminated program cc1
Please submit a full bug report, with preprocessed source (by using -freport-bug).
See <file:///usr/share/doc/gcc-15/README.Bugs> for instructions.
```


For the issues I've observed (referenced by the preceding message in this bug
report), I have listed some of my findings at the link below.
 * https://github.com/BrickBot/GNU-Legacy-Toolchain/issues/14

Briefly from that GitHub link, here is a short code snippet that will fail compilation:
``` C
struct S { ~S(); };
void bar();
void foo()
{
  S s;
  bar();
}
```


If I drop the optimization level from -O2 to -O1, the problems encountered
when using GCC 15 to build GCC 3.4.6 seem to go away.


Matthew