[jira] Commented: (MAPREDUCE-1166) SerialUtils.cc: dynamic allocation of arrays based on runtime variable is not portable

["Allen Wittenauer (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796473#action_12796473 ] 

Allen Wittenauer commented on MAPREDUCE-1166:
---------------------------------------------

So I spent some time looking at this today and trying to get this to work with VLAs in SunStudio.  Doing research, I ran across this:

http://forums.sun.com/thread.jspa?threadID=5348093

"C99 VLAs were discussed in the C++ Committee for possible inclusion in the next standard. The unanimous view was that they did not have nice properties (the word "suck" was bandied about), and that std::vector or other containers were a superior solution in C++ programming."

Thus, while __func__ works with CC -features=extensions, it doesn't appear that Sun Studio supports all of the C99 features in their C++ compiler.  This makes me wonder if using __func__ was the right thing to do now.

They also have an interesting discussion about alloca vs. malloc.



> SerialUtils.cc: dynamic allocation of arrays based on runtime variable is not portable
> --------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1166
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1166
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Allen Wittenauer
>            Assignee: Allen Wittenauer
>         Attachments: MAPREREDUCE-1166.patch
>
>
> In SerialUtils.cc, the following code appears:
>     int len;
>     if (b < -120) {
>       negative = true;
>       len = -120 - b;
>     } else {
>       negative = false;
>       len = -112 - b;
>     }
>     uint8_t barr[len];
> as far as I'm aware, this is not legal in ANSI C and will be rejected by ANSI compliant compilers.  Instead, this should be malloc()'d based upon the size of len and free()'d later.

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