Added support for simple pointer arithmetic. Fixes #434

[Konstantin8105]

Close #434
See #67

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This change is 

[Konstantin8105]

Not ready for review

[Konstantin8105]

Ready for review if Ok in travis

[elliotchance]

Reviewed 4 of 6 files at r1, 3 of 3 files at r2.
Review status: all files reviewed at latest revision, 2 unresolved discussions, some commit checks failed.

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transpiler/call.go, line 74 at r2 (raw file):

	// function stdlib.c
	if functionName == "calloc" && len(n.Children()) == 3 {

Can you be sure that len(n.Children()) == 3 means that there are 3 arguments? Maybe you should extract the arguments to be sure. I remember we had a function for returning a specific type of node, but I cannot remember where that code is now...

Something like this?

children := GetNodesOfType(n.Children(), (*ast.Something)(nil))
if functionName == "calloc" && len(children) == 3 {
    // children is not reliable even when the AST has other child nodes
    // that are not arguments.
}

It will make the code more robust if there are any extra children that are not arguments. Also you rely on indexes like 0 and 1 below but the actual parameters may not be located there, use children[0] instead to know it's correct.

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transpiler/unary.go, line 173 at r2 (raw file):

// Example of using:
// *(t + 1) = ...
func transpilePointerArith(n *ast.UnaryOperator, p *program.Program) (

This is really awesome! Does this also work with decrementing pointer arithmetic? Like the common loop: while (p-- != NULL) { }

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Comments from Reviewable

[elliotchance]

Review status: all files reviewed at latest revision, 2 unresolved discussions, some commit checks failed.

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transpiler/call.go, line 74 at r2 (raw file):

Previously, elliotchance (Elliot Chance) wrote…

Can you be sure that len(n.Children()) == 3 means that there are 3 arguments? Maybe you should extract the arguments to be sure. I remember we had a function for returning a specific type of node, but I cannot remember where that code is now...

Something like this?

children := GetNodesOfType(n.Children(), (*ast.Something)(nil))
if functionName == "calloc" && len(children) == 3 {
    // children is not reliable even when the AST has other child nodes
    // that are not arguments.
}

It will make the code more robust if there are any extra children that are not arguments. Also you rely on indexes like 0 and 1 below but the actual parameters may not be located there, use children[0] instead to know it's correct.

This is the method: https://github.com/elliotchance/c2go/blob/master/ast/traverse.go#L12

However, that is recursive. You may want to create a similar method that does not recursive.

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Comments from Reviewable

[Konstantin8105]

Review status: all files reviewed at latest revision, 2 unresolved discussions, some commit checks failed.

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transpiler/call.go, line 74 at r2 (raw file):

Previously, elliotchance (Elliot Chance) wrote…

This is the method: https://github.com/elliotchance/c2go/blob/master/ast/traverse.go#L12

However, that is recursive. You may want to create a similar method that does not recursive.

|   |   `-CallExpr 0x1dce580 <col:18, col:40> 'void *'
|   |     |-ImplicitCastExpr 0x1dce568 <col:18> 'void *(*)(unsigned long, unsigned long)' <FunctionToPointerDecay>
|   |     | `-DeclRefExpr 0x1dce4c8 <col:18> 'void *(unsigned long, unsigned long)' Function 0x1dce350 'calloc' 'void *(unsigned long, unsigned long)'
|   |     |-ImplicitCastExpr 0x1dce5b8 <col:25> 'unsigned long' <IntegralCast>
|   |     | `-IntegerLiteral 0x1dce4f0 <col:25> 'int' 5
|   |     `-UnaryExprOrTypeTraitExpr 0x1dce520 <col:27, col:39> 'unsigned long' sizeof 'float'

3 node:

1. for function identification
2. for amount of elements
3. for type size
   I suppose it is like ForStmt - it has 5 children.
   I will add more test for that point.

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transpiler/unary.go, line 173 at r2 (raw file):

Previously, elliotchance (Elliot Chance) wrote…

This is really awesome! Does this also work with decrementing pointer arithmetic? Like the common loop: while (p-- != NULL) { }

Now, it is not support

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Comments from Reviewable

[codecov]

Codecov Report

Merging #441 into master will increase coverage by 0.06%.
The diff coverage is 85%.

@@            Coverage Diff            @@
##           master    #441      +/-   ##
=========================================
+ Coverage   81.03%   81.1%   +0.06%     
=========================================
  Files         145     145              
  Lines        6434    6509      +75     
=========================================
+ Hits         5214    5279      +65     
- Misses        962     968       +6     
- Partials      258     262       +4

Impacted Files	Coverage Δ
transpiler/variables.go	81.92% <0%> (ø)	⬆️
program/program.go	80.28% <100%> (ø)	⬆️
types/resolve.go	76.19% <100%> (+0.38%)	⬆️
transpiler/call.go	69.23% <70.58%> (+0.18%)	⬆️
transpiler/unary.go	78.03% <91.07%> (+4.61%)	⬆️

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[elliotchance]

Reviewed 2 of 2 files at r3.
Review status: all files reviewed at latest revision, 1 unresolved discussion.

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tests/array.c, line 232 at r3 (raw file):

		is_true(arr != NULL);
		(void)(arr);
	}

Awesome!

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Comments from Reviewable