[BUG] ICE: not all comments were printed

[JohelEGP]

Minimal reproducer (https://godbolt.org/z/Y9sqcY1jG):

a: type = { }
c: a = (); //

Commands:

cppfront x.cpp2

Expected result: A well-formed program.

Actual result and error:

cppfront: $prefix/cppfront.cpp:1356: lower_to_cpp1_ret cpp2::cppfront::lower_to_cpp1(): Assertion `tokens.num_unprinted_comments() == 0 && "ICE: not all comments were printed"' failed.
Aborted (core dumped)

[filipsajdak]

The issue is related to source_position::lineno. In the following code:

a: type = { } // a
c: a = (); // b
i: int = 42;

Assertion is triggered. Adding extra line between c and i declaration:

a: type = { } // a
c: a = (); // b

i: int = 42;

Generates:

//=== Cpp2 type declarations ====================================================


#include "cpp2util.h"

#line 1 "/Users/filipsajdak/dev/execspec/external/tests/bug_344_ice.cpp2"
class a;

//=== Cpp2 type definitions and function declarations ===========================

#line 1 "/Users/filipsajdak/dev/execspec/external/tests/bug_344_ice.cpp2"
class a {public: a() = default; a(a const&) = delete; auto operator=(a const&) -> void = delete; };
extern a c;   // a
           // b
extern int i;
//=== Cpp2 function definitions =================================================


#line 2 "/Users/filipsajdak/dev/execspec/external/tests/bug_344_ice.cpp2"
a c {}; 

int i {42}; 

Please notice that comments are moved by one line - currently it is:

class a {public: a() = default; a(a const&) = delete; auto operator=(a const&) -> void = delete; };
extern a c;   // a
           // b

And it should be:

class a {public: a() = default; a(a const&) = delete; auto operator=(a const&) -> void = delete; };  // a
extern a c; // b

[filipsajdak]

When replace type definition with variable declaration:

j : int = 24; // a
i : int = 42;

It properly generates:

//=== Cpp2 type declarations ====================================================


#include "cpp2util.h"


//=== Cpp2 type definitions and function declarations ===========================

#line 1 "/Users/filipsajdak/dev/execspec/external/tests/bug_344_ice.cpp2"
extern int j; // a
extern int i;
//=== Cpp2 function definitions =================================================

#line 1 "/Users/filipsajdak/dev/execspec/external/tests/bug_344_ice.cpp2"
int j {24}; 
int i {42}; 

[filipsajdak]

Found solution and pushed PR: #351

[filipsajdak]

The same issue would happen for namespace definition:

a: namespace = { } // a
i : int = 42;

[filipsajdak]

ah... this case is not closed yet... I have fixed other ones :/

[filipsajdak]

OK, this issue is all about commenting on the last line of cpp2 on the global object definition. The problem is that when trying to publish comments during printer.finalize() call, the following condition is false:

phase == phase2_func_defs
&& pparser->is_within_function_body( comments[next_comment].start.lineno )

Quick fix removes ICE but put comment on phase2 (Cpp2 function definitions) and not on phase1 (Cpp2 type definitions and function declarations):

diff --git a/source/cppfront.cpp b/source/cppfront.cpp
index 99f83ac..248eb05 100644
--- a/source/cppfront.cpp
+++ b/source/cppfront.cpp
@@ -423,9 +423,12 @@ private:
                     ||
                     (
                         phase == phase2_func_defs
-                        && pparser->is_within_function_body( comments[next_comment].start.lineno )
-                        )
+                        && (
+                            pparser->is_within_function_body( comments[next_comment].start.lineno )
+                            || pos.lineno >= std::ssize(psource->get_lines())
+                            )
                     )
+                )
                 {
                     //  For a line comment, start it at the right indentation and print it
                     //  with a newline end

The earlier phase condition could pass:

phase == phase1_type_defs_func_decls
&& !pparser->is_within_function_body( comments[next_comment].start.lineno )

but the flow cannot get there as before it there is another condition that is false:

while (curr_pos.lineno < pos.lineno)

Because pos is exactly on the same line as curr_pos when it prints:

printer.print_cpp2( "extern ", n.position() );

[filipsajdak]

@JohelEGP After sleeping over it I found a solution that print comments in proper place and does not ruin all regression tests: #354

[hsutter]

Thanks for the bug reports and repros! These should all work now, please check...

[filipsajdak]

Happy to help.

I confirm that it works.