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digitalmars.D.bugs - [Issue 4323] New: std.demangle incorrectly handles template floating point numbers

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4323

           Summary: std.demangle incorrectly handles template floating
                    point numbers
           Product: D
           Version: D1 & D2
          Platform: Other
        OS/Version: Mac OS X
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: doob me.com


--- Comment #0 from Jacob Carlborg <doob me.com> 2010-06-15 11:38:04 PDT ---
According to the ABI spec the mangled form of template floating point numbers
looks like this:

Value:
    e HexFloat

HexFloat:
    N HexDigits P Exponent
    HexDigits P Exponent

But std.demnalge doesn't seem to handle the exponent, it doesn't handle the
'P'. The unittests that test this are also incorrect. The first one looks like
this:

mangled form:
_D4test58__T9factorialVde67666666666666860140VG5aa5_68656c6c6fVPvnZ9factorialf

demangled form:
float test.factorial!(double 4.2, char[5] \"hello\"c, void* null).factorial

As far as I can see the mangled form doesn't follow the spec or what dmd
produces.

module test;

float factorial (T...) ()
{
    return float.init;
}

void main ()
{
    factorial!(4.2, "hello", null);
}

Compiling the above code and running the "nm" command on the resulting binary
shows that "factorial" with the above given values is mangled as:
_D4test57__T9factorialVde8666666666666667PN1VAyaa5_68656c6c6fVPvnZ9factorialFZf

After all the 6s the is a 7 and then a P. In the std.demangle unittest the P is
missing, also at the end of the mangled name is a Z which is missing in the
unittest.

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4323


kennytm gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kennytm gmail.com


--- Comment #1 from kennytm gmail.com 2011-05-08 02:14:35 PDT ---
With core.demangle it now resolves
_D4test57__T9factorialVde8666666666666667PN1VAyaa5_68656c6c6fVPvnZ9factorialFZf
into:

float test.factorial!(8.400000, "hello", null).factorial()

The only problem is the floating point number is 2 times bigger than the
expected.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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kennytm gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch, wrong-code
          Component|Phobos                      |druntime


--- Comment #2 from kennytm gmail.com 2011-05-08 02:45:28 PDT ---
The demangler forgot to put the 'p', making the exponent part totally ignored.
Also, using the '%f' format makes floating point number that is extremely small
becomes 0.00000. I think '%g' is more suitable.


diff --git a/src/core/demangle.d b/src/core/demangle.d
index 6d37633..b2ab00d 100644
--- a/src/core/demangle.d
+++ b/src/core/demangle.d
   -368,6 +368,7    private struct Demangle
             next();
         }
         match( 'P' );
+        tbuf[tlen++] = 'p';
         if( 'N' == tok() )
         {
             tbuf[tlen++] = '-';
   -386,7 +387,7    private struct Demangle
         tbuf[tlen] = 0;
         debug(info) printf( "got (%s)\n", tbuf.ptr );
         val = strtold( tbuf.ptr, null );
-        tlen = snprintf( tbuf.ptr, tbuf.length, "%Lf", val );
+        tlen = snprintf( tbuf.ptr, tbuf.length, "%Lg", val );
         debug(info) printf( "converted (%.*s)\n", cast(int) tlen, tbuf.ptr );
         put( tbuf[0 .. tlen] );
     }

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--- Comment #3 from kennytm gmail.com 2011-05-08 09:47:59 PDT ---
druntime pull request #15

https://github.com/D-Programming-Language/druntime/pull/15

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kennytm gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|D1 & D2                     |D1


--- Comment #4 from kennytm gmail.com 2011-06-19 11:41:14 PDT ---
Fixed for D2 in
https://github.com/D-Programming-Language/druntime/commit/f9ce91691092281a2c07699cfd68fd1297c7b37f.

Not sure about D1.

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