Corrupted characters in {-9223372036854775808}

[tueda]

The preprocessor calculator prints the minimum negative number wrongly.

* for 64-bits version
#message {-9223372036854775808}
.end

FORM 4.2.0 (Jul 11 2017, v4.2.0-8-ga8b9963) 64-bits  Run: Wed Jul 12 14:22:11 2017

~~~-(

Presumably for the same reason as in #139.

[tueda]

Failed with clang?? https://travis-ci.org/tueda/form/builds/253705758 (See Issue219.)

[vermaseren]

I am not quite sure what you mean with this. On the apple my fix worked. Jos

…

On 15 jul. 2017, at 19:28, Takahiro Ueda ***@***.***> wrote: Failed with clang?? https://travis-ci.org/tueda/form/builds/253705758 <https://travis-ci.org/tueda/form/builds/253705758> (See Issue219.) — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#219 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFLxEl68SGltY3d7AIHR2YKuPQTTK6iuks5sOPaggaJpZM4OVjKn>.

[tueda]

It seems that the following code gave an error with clang in macOS on Travis CI:

#$n64  = -2^63;
L F64  = {`$n64'};
P;
.end

[tueda]

You need to turn on the optimization. Probably something hits on an undefined behaviour, which compilers are allowed to discard smartly. In the following link you can play with "Run" with/without "Optimization": https://wandbox.org/permlink/Bhe1uTtaJ4niW9Z5

[tueda]

I guess

if ( answer < 0 ) { answer = -answer; }

is already undefined for answer=-9223372036854775808 (overflow in signed arithmetic). See https://godbolt.org/g/oX98bo, in which gcc completely skips a conditional branch with -O1.