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

["Eli Collins (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12790615#action_12790615 ] 

Eli Collins commented on MAPREDUCE-1166:
----------------------------------------

Hey Allen, 

Does this code not compile on solaris? Perhaps the build is just not passing -xc99.

>From quickly looking at the code it looks like len will never be greater than 8 in which case an appropriate assert/check could be added and the allocation could read:
{code}
uint8_t barr[sizeof(int64_t)];
{code}

The disadvantages of alloca (http://www.gnu.org/s/libc/manual/html_node/Disadvantages-of-Alloca.html) don't apply here but it doesn't seem necessary either.

Thanks,
Eli

> 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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