[jira] [Comment Edited] (ARROW-2668) [C++] -Wnull-pointer-arithmetic warning with dlmalloc.c on clang 6.0, Ubuntu 14.04

["Wes McKinney (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-2668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16499245#comment-16499245 ] 

Wes McKinney edited comment on ARROW-2668 at 6/3/18 12:51 AM:
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It looks like this warning was relatively recently added to LLVM https://reviews.llvm.org/D37042. We are using clang-format-6 in our Travis CI but not using clang itself when compiling which is probably why this issue hasn't come up yet


was (Author: wesmckinn):
It looks like this warning was relatively recently added to LLVM https://reviews.llvm.org/D37042

> [C++] -Wnull-pointer-arithmetic warning with dlmalloc.c on clang 6.0, Ubuntu 14.04 
> -----------------------------------------------------------------------------------
>
>                 Key: ARROW-2668
>                 URL: https://issues.apache.org/jira/browse/ARROW-2668
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++
>    Affects Versions: 0.9.0
>            Reporter: Wes McKinney
>            Priority: Major
>             Fix For: 0.10.0
>
>
> I encountered this failure with {{-Werror}} on a nearly fresh Ubuntu 14.04 install using clang-6 from LLVM apt
> {code}
> ../src/plasma/thirdparty/dlmalloc.c:3504:68: error: arithmetic on a null pointer treated as a cast from integer to pointer is a GNU extension [-Werror,-Wnull-pointer-arithmetic]
>       size_t mfree = m->topsize + (((((size_t)(((void*)((char*)(0) + ((sizeof(size_t))<<1)))) & (((size_t)(2 * sizeof(void *))) - ((size_t)1))) == 0)? 0 : ((((size_t)(2 * sizeof(void *))) - ((size_t)(((void*)((char*)(0) + ((sizeof(size_t))<<1)))) & (((size_t)(2 * sizeof(void *))) - ((size_t)1)))) & (((size_t)(2 * sizeof(void *))) - ((size_t)1))))+(((sizeof(struct malloc_segment)) + ((sizeof(size_t))) + (((size_t)(2 * sizeof(void *))) - ((size_t)1))) & ~(((size_t)(2 * sizeof(void *))) - ((size_t)1)))+(((sizeof(mchunk)) + (((size_t)(2 * sizeof(void *))) - ((size_t)1))) & ~(((size_t)(2 * sizeof(void *))) - ((size_t)1))));
> {code}
> See gist for complete log https://gist.github.com/wesm/61ee3592045bfaf390d5d4557f3c5a22



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