Segmentation fault in DMD - how to debug?

[Dennis]

On Tuesday, 4 October 2022 at 02:13:16 UTC, Walter Bright wrote:
> grep reveals:
>
> https://github.com/dlang/dmd/pull/14517

I have a few more :)

The backend has 4 calls to `util_malloc`, 28 calls to 
`mem_malloc`, 2 calls to `mem_malloc2`, 8 calls to `mem_fmalloc` 
(why so many `malloc` wrappers?), and 16 calls to `mem_calloc`. I 
don't see any checks on those.

Here's one with plain `malloc`:

dmd/backend/dcgcv.d:264
```
d = cast(debtyp_t *) malloc(debtyp_t.sizeof - (d.data).sizeof + 
length);
d.length = cast(ushort)length;
```

This one checks, but after memcpy'ing to `null`!

dmd/common/file.d:148
```
name = cast(char*) memcpy(malloc(totalNameLength), filename, 
totalNameLength);
name || assert(0, "FileMapping: Out of memory.");
```