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Disable strict aliasing on clang #25067

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Disable strict aliasing on clang #25067

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@bptato bptato commented Jul 22, 2025

Workaround for #24596.

I also took the liberty to disable it on all targets with GCC, since their documentation claims that it is also enabled on -Os.

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Disable strict aliasing on clang
2ceea76 
Workaround for nim-lang#24596.

I also took the liberty to disable it on all targets with GCC, since
their documentation claims that it is also enabled on -Os.
bptato added a commit to bptato/Nim that referenced this pull request Jul 23, 2025
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Confrom to standard C's strict aliasing rules in seqs_v2
9362878 
Alternative to nim-lang#25067; fixes nim-lang#24596.

Pros:
* No codegen changes needed.
* No negative changes in generated code size.
* Works with all standard-conforming C compilers - conceptually, memcpy
  treats both structs as character types, which are compatible with
  all types.

Cons: it's very ugly.
@bptato bptato mentioned this pull request Jul 23, 2025
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@bptato bptato mentioned this pull request Aug 21, 2025
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@Araq Araq closed this Sep 10, 2025
@Araq Araq reopened this Sep 10, 2025
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Araq commented Sep 11, 2025

CI fails with some super weird changes in the stack tracing. No idea, ping @ringabout

@Araq Araq closed this Sep 12, 2025
@Araq Araq reopened this Sep 12, 2025
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I think it marks a real issue of the change, though I have no clue for now

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ringabout commented Sep 12, 2025 •
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It seems that some C warnings disturbing the output comparing of testament, which causes CI to fail. I guess warnings are needed to be suppressed somehow

+/home/vsts/.cache/nim/trunnableexamples_d/runnableExamples/@[email protected]:163:291: warning: initialization discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
2025-09-12T13:29:12.4470025Z +  163 | N_LIB_PRIVATE TNimTypeV2 NTIv2__4rjmsYJxlo49cXH3mEZVmZg_ = {.destructor = ((void*) rttiDestroy__systemZexceptions_u56), .size = sizeof(tyObject_OverflowDefect__4rjmsYJxlo49cXH3mEZVmZg), .align = ((NI16) NIM_ALIGNOF(tyObject_OverflowDefect__4rjmsYJxlo49cXH3mEZVmZg)), .depth = 4, .display = TM__TzI3paKQY09cLjc9cmCvur3A_3, .traceImpl = ((void*) eqtrace___system_u5268), .flags = 0};
2025-09-12T13:29:12.4470814Z +      |                                                                                                                                                                                                                                                                                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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@bptato @Araq @ringabout