https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115912
--- Comment #18 from Sam James <sjames at gcc dot gnu.org> ---
The first point of divergence seems to be:
good:
```
(gdb) p unmapped_range
$59 = {minimum = -0.66668701171875, middle = 0, maximum = 0.4000244140625}
(gdb) n
231 if (mapping.must_include ())
(gdb) p mapping
$60 = <optimized out>
(gdb) n
233 value_mappings.push (mapping);
(gdb) p value
$61 = true
(gdb) p value_mappings
$62 = {allocated = 8, length = 1, arrayZ = 0x690be0}
(gdb) p *value_mappings.arrayZ
$63 = {coords = {{<OT::IntType<short, 2>> = {v = {v = "\340\001"}}, <No data
fields>}, {<OT::IntType<short, 2>> = {v = {v = "\327", <incomplete sequence
\330>}}, <No data fields>}},
static null_size = 4, static min_size = 4, static static_size = 4}
(gdb)
```
bad:
```
233 value_mappings.push (mapping);
(gdb) p value_mappings
$66 = {allocated = 8, length = 1, arrayZ = 0x690be0}
(gdb) p value_mappings.arrayZ
$67 = (OT::AxisValueMap *) 0x690be0
(gdb) p *value_mappings.arrayZ
$68 = {coords = {{<OT::IntType<short, 2>> = {v = {v = "\340\001"}}, <No data
fields>}, {<OT::IntType<short, 2>> = {v = {v = "\377\377"}}, <No data
fields>}}, static null_size = 4,
static min_size = 4, static static_size = 4}
(gdb)
```
i.e. arrayZ gets corrupted?
