[stlport-bugs] [ stlport-Bugs-1771153 ] _Stl_atod crash in MSVC2005 with Smaller Type Check

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Bugs item #1771153, was opened at 2007-08-09 14:31
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Category: General code
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Michel Donais (cpct0)
Assigned to: Nobody/Anonymous (nobody)
Summary: _Stl_atod crash in MSVC2005 with Smaller Type Check

Initial Comment:
num_get_float.cpp, line #522 and up

    /* Round to 53 bits */
    rest = value & (1<<10)-1;
    value >>= 10;
#if !defined(__SC__)
    guard = (uint32) value & 1;
#else    //*TY 03/25/2000 -
    guard = to_ulong(value & 1);
#endif

The line (526): guard = (uint32) value & 1;
Should read : guard = (uint32)( value & 1 );

Under MSVC2005, with Smaller Type Check compiler option on, the line might have a large value, and will execute the conversion to (uint32) before the bitwise-and &, meaning under cases where the dc is bigger than a uint32, it will assert.

Added study: This has the advantage of being numerically valid, as currently the compiler has to assume the uint32 value is getting plainly truncated. However, this has the disadvantage of doing a potential asm "load high 32 bits of value" followed by a "and to 0", while using a useless always-zero second register/memory variable. To make it execute in MSVC2005, I find this a small price to pay.

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