Re: gcc -O2 produces faulty code : gcc 3.0.3 and gcc 3.0.4

[Russell Ruby <russ at MATH dot ORST dot EDU>]

I forgot to mention:

For what it's worth, I also compiled the xlhtml package with the
Sun workshop 6 (forte) compiler at the highest level of optimization,
"-xO5", and it produces correct output for integer cell values.
(The usual -xO2 works fine too).
Consequently, "gcc -O2" seems more likely to be the culprit rather than
something strange in the xlhtml.c source which is being optimized away.
And even if so, the Sun compiler was smart enough not to do so :)

russ

>
>Systems:
>
>  Sparc Solaris 8 with gcc 3.0.3 and gcc 3.0.4
>and
>  IBM AIX with unknown version of gcc
>
>Problem description:
>
>xlhtml is a package (see last paragraph) which renders microsoft
>97/2000 excel documents into html.
>
>When compiled with optimization "-O2", xlhtml renders integers
>entered as "general" cell values in excel97/2000 spread sheets as
>garbage floating point numbers, e.g. "6.95357380974837e-310".
>
>However, if all the source files in the xlhtml-0.4.9.0 distribution
>except xlhtml.c are still compiled with "-O2", but xlhtml.c is
>compiled with either no optimization or "-O", then integer cell entries
>are correctly written as integers in the html output.
>
>For example, here is a snippet of html output when xlhtml.c
>is compiled with "-O2".
>
><TR VALIGN="bottom">
><TD>Waymire</TD>
><TD>6.95357380974822e-310</TD>
><TD>A-J</TD>
><TD>KIDDER 364</TD>
><TD>Rabimov</TD>
><TD>6.95357380974832e-310</TD>
><TD>6.95357380974837e-310</TD>
><TD>&nbsp;</TD>
><TD>&nbsp;</TD>
><TD>&nbsp;</TD>
></TR>
>
>Here is the same output section when xlhtml.c is compiled as "-O",
>
><TR VALIGN="bottom">
><TD>Waymire</TD>
><TD>20</TD>
><TD>A-J</TD>
><TD>KIDDER 364</TD>
><TD>Rabimov</TD>
><TD>61</TD>
><TD>119</TD>
><TD>&nbsp;</TD>
><TD>&nbsp;</TD>
><TD>&nbsp;</TD>
></TR>
>
>My apologies for not supplying a succinct C source code
>example demonstrating the problem.  From experimenting by
>changing individual bytes in the six byte chunks in excel
>documents corresponding to "general" integer value cells,
>what happens would be consistent with pointer arithmetic/dereferencing
>getting out of whack under "-O2", but that is just a lame guess.
>Again, the problem is in the file xlhtml.c, and not in the "cole" library
>which is used to parse and read the "file system" embodied in the
>actual excel "xls" file.
>
>The package xlhtml-0.4.9.0 is normally available from www.xlhtml.org,
>but since it is temporarily offline because of hardware problems,
>I have placed the source package on our anonymous ftp site as:
>  ftp://ftp.math.orst.edu/pub/xlhtml-0.4.9.0.tar.gz
>
>thanks,
>
>Russell Ruby   russ@math.orst.edu
>