Answer by BЈовић for Generate the longest error message in C++

19 characters

Create a file a.cpp with this content :

#include __FILE__p;

Compile as :

g++ a.cpp

and get amazing 21300 lines error messages :

In file included from a.cpp:1:0,                 from a.cpp:1,                 from a.cpp:1,                 from a.cpp:1,

...

... 21280 error lines ...
...

In file included from a.cpp:1:0,                 from a.cpp:1,                 from a.cpp:1,                 from a.cpp:1,                 from a.cpp:1:a.cpp:2:1: error: ‘p’ does not name a typeIn file included from a.cpp:1:0,                 from a.cpp:1,                 from a.cpp:1,                 from a.cpp:1:a.cpp:2:1: error: ‘p’ does not name a typeIn file included from a.cpp:1:0,                 from a.cpp:1,                 from a.cpp:1:a.cpp:2:1: error: ‘p’ does not name a typeIn file included from a.cpp:1:0,                 from a.cpp:1:a.cpp:2:1: error: ‘p’ does not name a typeIn file included from a.cpp:1:0:a.cpp:2:1: error: ‘p’ does not name a typea.cpp:2:1: error: ‘p’ does not name a type