Created attachment 33015 [details]
The source and .i and others required by the instructions.

This code:

#include <stdio.h>

int main() {
    long long sm = 0x7FFFFFFFFFFFFFFF;
    double dm = (double)sm;
    double value = 9223372036854775800.0;
    printf("%s\n", (((double)sm) == value ? "true" : "false"));
    printf("%s\n", (dm ==           value ? "true" : "false"));
}

causes the problem.
One would expect that both lines of output would be the same, but the bug causes
the output to be
false
true

The bug occurs in gcc version 4.8.2 on the 32-bit Intel version of Kubuntu 14.04.
It also occurs in g++ version 4.8.2 on the same system, and on other current and recent 32-bit Intel releases of Kubuntu and Fedora with various versions of g++ 4.7 and 4.8.

The bug does not occur in g++ on any 64-bit Intel system I tried, with versions 4.7.* and 4.8.*.
The bug does not occur in g++ on a 32-bit ARM system (Chromebook) running Gentoo and g++ version 4.8.2.

Furthermore, the bug does not occur in gcc or g++ version 4.9.0 on the 32-bit version of Kubuntu 14.04.
Was the bug fixed by accident or purposefully?  I couldn't find any mention of the bug in the database.

Perhaps the only actions needed are to figure out why the bug occurs in earlier versions, and add a regression test to make sure it doesn't recur.

A .tar.bz2 file containg the relevant files is attached.