for (;;) is legal C, but currently causes a panic. Fo

Side note: why is there an extra <<<NULL>>&gt

panic on empty for-loop conditions about c2go HOT 3 CLOSED

elliotchance commented on August 23, 2024

panic on empty for-loop conditions

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Comments (3)

jnjackins commented on August 23, 2024

It looks like there needs to be some special casing around handling of null nodes during AST parsing.

If I comment out the section of main.go that removes <<<NULL>>> from the AST, then I get the following, for for(;;) print("foo"):

|   `-ForStmt 0x7fd828076c18 <line:3:2, col:19>
|     |-<<<NULL>>>
|     |-<<<NULL>>>
|     |-<<<NULL>>>
|     |-<<<NULL>>>
|     `-CallExpr 0x7fd828076bd0 <col:11, col:19> 'int'
|       |-ImplicitCastExpr 0x7fd828076bb8 <col:11> 'int (*)()' <FunctionToPointerDecay>
|       | `-DeclRefExpr 0x7fd828076b08 <col:11> 'int ()' Function 0x7fd828076a60 'print' 'int ()'
|       `-ImplicitCastExpr 0x7fd828076c00 <col:17> 'char *' <ArrayToPointerDecay>
|         `-StringLiteral 0x7fd828076b68 <col:17> 'char [1]' lvalue ""

And the following for for(1;1;1) print("foo"):

|   `-ForStmt 0x7fad58076c78 <line:3:2, col:22>
|     |-IntegerLiteral 0x7fad58076a40 <col:7> 'int' 1
|     |-<<<NULL>>>
|     |-IntegerLiteral 0x7fad58076a60 <col:9> 'int' 1
|     |-IntegerLiteral 0x7fad58076a80 <col:11> 'int' 1
|     `-CallExpr 0x7fad58076c30 <col:14, col:22> 'int'
|       |-ImplicitCastExpr 0x7fad58076c18 <col:14> 'int (*)()' <FunctionToPointerDecay>
|       | `-DeclRefExpr 0x7fad58076b68 <col:14> 'int ()' Function 0x7fad58076ac0 'print' 'int ()'
|       `-ImplicitCastExpr 0x7fad58076c60 <col:20> 'char *' <ArrayToPointerDecay>
|         `-StringLiteral 0x7fad58076bc8 <col:20> 'char [1]' lvalue ""

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jnjackins commented on August 23, 2024

Side note: why is there an extra <<<NULL>>> in both cases?

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elliotchance commented on August 23, 2024

That's a good question, I don't know what the extra <<<NULL>>> are supposed to mean, but I ignore them when parsing: https://github.com/elliotchance/c2go/blob/master/main.go#L26-L30

This always gives me three parts for the for loop: https://github.com/elliotchance/c2go/blob/master/for_stmt.go#L30-L32

However, as you say, if there are less than three parts then that code would not work. Mind submitting a patch with the test C file?

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