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digitalmars.D.bugs - BUGs: Nested function problems

reply h3r3tic <foo bar.baz> writes:
Now this bug is interesting :>
I have a function taking some parameters, yet this function doesn't do 
anything directly. Instead it calls a nested function which in turn 
doesn't take any parameters. Now, the standard says " Nested functions 
have access to the variables and other symbols defined by the lexically 
enclosing function". This probably applies as well to the enclosing 
function's parameters as they are visible in the nested function.
However, in a very specific case, the data that the nested function 
accesses is somehow corrupted.
On the other hand, if I pass every parameter of the enclosing function 
to the nested one, the data is just fine.
The source for the bug is quite longish, yet I was unable to reduce its 
size any further. The function of interest is "extractTriangles". It 
contains a nested function "foobar". The code compiles and when ran, an 
exception is caught.
Now, when the nested function is removed (and its contents are moved to 
the enclosing function), the program runs just fine. It doesn't really 
matter what it does, the fact is that the variable "geomObj.name" 
contains invalid data, whilst it should contain text "NODE".

That's one thing. Another is that the nested 'foobar' function contains 
a try-catch block:
	void foobar()
	{
		try
		{
			writefln("name: ", geomObj.name);
			return;		
			geomObj.mesh.faces[0].a - geomObj.xlate;
		}
		catch(Object err)
		{
			throw err;
		}
	}

When the try and catch statements are removed like this:
	void foobar()
	{
			writefln("name: ", geomObj.name);
			return;		
			geomObj.mesh.faces[0].a - geomObj.xlate;
	}

And I compile with "-inline", then the compile result looks like this:

 Internal error: e2ir.c 615


But wait, that's not all... the internal error disappears when I leave 
the scope of the try block in place like this:
	void foobar()
	{
		{
			writefln("name: ", geomObj.name);
			return;
			geomObj.mesh.faces[0].a - geomObj.xlate;
		}
	}

But then I've got the original runtime exception as with try and catch


Here's the source:

// ------------------------------------------------------------

private import std.stdio;


struct vec3
{
	vec3 opSub(vec3 a)
	{
		vec3 x;
		return x;
	}
}

struct Face
{
	vec3	a;
}

struct Mesh
{
	Face[]	faces;
}
	
struct GeomObject
{
	Mesh	mesh;
	char[]	name;
	vec3		xlate;
}

class AseLoader
{
	this()
	{
		GeomObject go;
		go.name = "NODE";
		geomObjects ~= go;
	}
	
	GeomObject[]	geomObjects;
}


void extractTriangles(GeomObject geomObj)
{
	void foobar()
	{
		try
		{
			writefln("name: ", geomObj.name);

			return;  // avoid accessing the array with 0 elements in the next line			
			geomObj.mesh.faces[0].a - geomObj.xlate;  // when this line is 
removed, the bug doesn't appear
		}
		catch(Object err)
		{
			throw err;
		}
	}
	
	foobar();
}

void main()
{
	try
	{
		AseLoader al = new AseLoader;
	
		foreach(GeomObject go; al.geomObjects)
		{
			writefln("processing ", go.name);
			extractTriangles(go);
		}
	} catch(Object err)
	{
		writefln("Exception caught: ", err);
	}
	
	getchar();
}

// -----------------------------------------

Program output:
	processing NODE
	name: Exception caught: invalid UTF-8 sequence

// -----------------------------------------

My system:
DMD.109
WinXP SP2 EN
Dec 26 2004
parent reply "Simon Buchan" <talk n.g> writes:
On Sun, 26 Dec 2004 19:04:40 +0100, h3r3tic <foo bar.baz> wrote:


 Now this bug is interesting :>
 I have a function taking some parameters, yet this function doesn't do
 anything directly. Instead it calls a nested function which in turn
 doesn't take any parameters. Now, the standard says " Nested functions
 have access to the variables and other symbols defined by the lexically
 enclosing function". This probably applies as well to the enclosing
 function's parameters as they are visible in the nested function.
 However, in a very specific case, the data that the nested function
 accesses is somehow corrupted.
 On the other hand, if I pass every parameter of the enclosing function
 to the nested one, the data is just fine.
 The source for the bug is quite longish, yet I was unable to reduce its
 size any further. The function of interest is "extractTriangles". It
 contains a nested function "foobar". The code compiles and when ran, an
 exception is caught.


note: I only got this when compiled with -inline, and without -g.


 Now, when the nested function is removed (and its contents are moved to
 the enclosing function), the program runs just fine. It doesn't really
 matter what it does, the fact is that the variable "geomObj.name"
 contains invalid data, whilst it should contain text "NODE".

 That's one thing. Another is that the nested 'foobar' function contains
 a try-catch block:
 	void foobar()
 	{
 		try
 		{
 			writefln("name: ", geomObj.name);
 			return;		
 			geomObj.mesh.faces[0].a - geomObj.xlate;
 		}
 		catch(Object err)
 		{
 			throw err;
 		}
 	}

 When the try and catch statements are removed like this:
 	void foobar()
 	{
 			writefln("name: ", geomObj.name);
 			return;		
 			geomObj.mesh.faces[0].a - geomObj.xlate;
 	}

 And I compile with "-inline", then the compile result looks like this:
  > Internal error: e2ir.c 615

 But wait, that's not all... the internal error disappears when I leave
 the scope of the try block in place like this:
 	void foobar()
 	{
 		{
 			writefln("name: ", geomObj.name);
 			return;
 			geomObj.mesh.faces[0].a - geomObj.xlate;
 		}
 	}

 But then I've got the original runtime exception as with try and catch


confirmed the above (same system)

Note that simply nothing is printed on a UTF-8 capable console. (tested on
both Widows (sic) and my editors console)

Obviously, this is a DMD specific inlining error.


 // -----------------------------------------

 My system:
 DMD.109
 WinXP SP2 EN
Dec 28 2004
parent "Thomas Kuehne" <thomas-dloop kuehne.cn> writes:
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Added to DStress as
http://dstress.kuehne.cn/run/bug_20041226_A.d
http://dstress.kuehne.cn/run/bug_20041226_B.d
http://dstress.kuehne.cn/run/bug_20041226_C.d
http://dstress.kuehne.cn/run/bug_20041226_D.d
http://dstress.kuehne.cn/run/bug_20041226_E.d

Note: this seems to be a Windows specific DMD bug

Thomas

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Dec 30 2004