Re: regression on zOS between 5.4.8 to 5.5.0 on zOS

On 2/6/2026 5:13 PM, Eric Covener wrote:
> We are on the old/traditional native xlc. Our HTTPD (+prereqs) port is
> somewhat old (~2005), so we are not using any of the more modern
> porting-friendly compilers or options.

Interesting.

I spent time testing 5.5.0 on older z/OS images w/ 'V1.10 XL C/C++',
'V2.4 XL C/C++', and 'C/C++ for Open Enterprise Languages on z/OS 2.0.0,
clang version 14.0.0' and could not replicate this issue (note: all
older z/OS compilers).

Given that your Lua compiler listing output resembles what happens when
using older nvidia C/C++ compilers[1], I would experiment with making
the temp variable in dischargevars[2] volatile to see if things improve.
Although, given that prior releases of Lua work for you, I would be
surprised if it did.

In nvc's case, everything in testes/ passes after applying that
universal band-aid/hack.

[1] For reference, compiling lcode.c (w/ HEAD at c6b484823) using nvc
22.11-0 will emit for [2]:

     199f:       ff 24 c5 00 00 00 00    jmp    *0x0(,%rax,8) // VLOCAL 
to 19AD
     ....:
     19ad:       41 c7 06 08 00 00 00    movl   $0x8,(%r14)  // VNONRELOC
     19b4:       e9 d9 02 00 00          jmp    1c92 
<luaK_dischargevars+0x312>
     ....:
     1c92:       48 83 c4 08             add    $0x8,%rsp // Function 
epilogue

Meanwhile, with nvc 26.1-0:

     1a1f:       ff 24 c5 00 00 00 00    jmp    *0x0(,%rax,8) // VLOCAL 
to 1A2D
     ....:
     1a2d:       0f b6 43 08             movzbl 0x8(%rbx),%eax
     1a31:       89 43 08                mov    %eax,0x8(%rbx)
     1a34:       c7 03 08 00 00 00       movl   $0x8,(%rbx) // VNONRELOC
     1a3a:       e9 ce 02 00 00          jmp    1d0d 
<luaK_dischargevars+0x30d>
     ....:
     1d0d:       48 83 c4 08             add    $0x8,%rsp // Function 
epilogue

AFIAK this was fixed in nvhpc-23-1.

[2] 
https://github.com/lua/lua/blob/c6b484823806e08e1756b1a6066a3ace6f080fae/lcode.c#L829

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