Bug 19148 – Alignment of section does not reflect the maximum alignment of its contents

This cause ldc compiled with dmd to crash, because of an unaligned SIMD instruction.

Whops, not the problem. But ldc still crashes, looking into it...

Looks like dmd mis-aligned a __gshared variable. .alignof reports an alignment of 16 bytes, while the variable is aligned only to 8 bytes.

I found the actual bug in codegen. In elfobj.c data_start(), when a symbol doesn't have a explicit alignment (Salignment <= 0), the symbol itself is aligned, but its section's alignment is not updated. To reproduce: __gshared real x; pragma(msg, x.alignof); Compiling it prints: 16LU, but the .data section of the resulting object file is only aligned to 8 bytes.

Which ldc and DMD versions? Does the just-released LDC 1.11 have this problem?

(In reply to Joakim from comment #4) > Which ldc and DMD versions? Does the just-released LDC 1.11 have this > problem? Most recent ldc release fix the build problem. But this is a dmd bug nonetheless. This bug still exists in dmd master

There was an issue with a ldc header mismatch that kinke found when merging the 2.081 frontend into ldc: are you sure that's not what you're seeing instead? https://github.com/ldc-developers/ldc/pull/2752#issuecomment-398897813 https://github.com/ldc-developers/ldc/pull/2752#issuecomment-399691107 It's a known bug that DMD 2.081 won't build a working ldc 1.10, have to use 1.11.

(In reply to Joakim from comment #6) > There was an issue with a ldc header mismatch that kinke found when merging > the 2.081 frontend into ldc: are you sure that's not what you're seeing > instead? > > https://github.com/ldc-developers/ldc/pull/2752#issuecomment-398897813 > https://github.com/ldc-developers/ldc/pull/2752#issuecomment-399691107 > > It's a known bug that DMD 2.081 won't build a working ldc 1.10, have to use > 1.11. I have inspected the generated binary, and found problem in DMD's code. This bug is real. Please read comment #3

OK, if you're so sure it's a problem in dmd's backend, a pull request is welcome.

(In reply to Joakim from comment #8) > OK, if you're so sure it's a problem in dmd's backend, a pull request is > welcome. While I know where the problem is, I don't know what is the proper fix. So I would need some help.

THIS ISSUE HAS BEEN MOVED TO GITHUB https://github.com/dlang/dmd/issues/19475 DO NOT COMMENT HERE ANYMORE, NOBODY WILL SEE IT, THIS ISSUE HAS BEEN MOVED TO GITHUB