Strange bug - GCC does not detect existing member of board

[ZirconiumX]

In my MakeMove function (copy-make based):

Code: Select all

#include "board.h"
#include "makemove.h"

int CastlingMask[128] = {
	11, 16, 16, 16,  3, 16, 16,  7, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	14, 16, 16, 16, 12, 16, 16, 13, 16, 16, 16, 16, 16, 16, 16, 16
};

Position * MakeMove(Position * Pos, int Move)
{
	int from = Move & 0x7F;
	int dest = (Move >> 7) & 0x7F;
	int flag = Move >> 14;

   // Off the board testing in case my move generator has a bug
	if (from & 0x88 || dest & 0x88)
		Pos->Valid = 0;

	Pos->Board[dest] = Pos->Board[from];
	Pos->Board[from] = Nothing;

	Pos->WhiteToMove ^= 1;

   // Castling, idea borrowed from DanaSah
	Pos->Castling &= CastlingMask[from] & CastlingMask[dest];

   // Promotion
	if (flag) {
		if (flag == 1)
			Pos->Board[dest] = (Pos->Board[dest] == WhitePawn) ? WhiteQueen : BlackQueen;
		if (flag == 2)
			Pos->Board[dest] = (Pos->Board[dest] == WhitePawn) ? WhiteRook : BlackRook;
		if (flag == 3)
			Pos->Board[dest] = (Pos->Board[dest] == WhitePawn) ? WhiteBishop : BlackBishop;
		if (flag == 4)
			Pos->Board[dest] = (Pos->Board[dest] == WhitePawn) ? WhiteKnight : BlackKnight;
	}

   // En Passant square, not yet tested
	if (Pos->Board[dest] == WhitePawn && dest - from == 32)
		Pos->EnPassant = from + 16;
	else if (Pos->Board[dest] == BlackPawn && from - dest == 32)
		Pos->EnPassant = dest + 16;
	else Pos->EnPassant = 255; // Since we're using a 128 element board, 255 is obviously off the board

	return Pos;
}

GCC 4.9.1 prints:

Code: Select all

makemove.c: In function 'MakeMove':
makemove.c:22:6: error: 'Position' has no member named 'Valid'
   Pos->Valid = 0;
      ^

when my Position structure quite clearly does have a member named 'Valid' defined in board.h

Code: Select all

#ifndef BOARD
#define BOARD

typedef struct {
	int Board[128];
	int WhiteToMove;
	int Castling; // KQkq
	int EnPassant;
	int Halfmove;
	int Valid; // Here is what GCC does not see.
} Position;

static const int Black = 0;
static const int White = 1;

static const int Nothing = 0;

static const int WhitePawn = 1;
static const int WhiteKnight = 2;
static const int WhiteBishop = 3;
static const int WhiteRook = 4;
static const int WhiteQueen = 5;
static const int WhiteKing = 6;

static const int BlackPawn = 7;
static const int BlackKnight = 8;
static const int BlackBishop = 9;
static const int BlackRook = 10;
static const int BlackQueen = 11;
static const int BlackKing = 12;

Position * ReadFEN(char * FEN);

#endif

I'm very confused, so I wonder if any of you can make sense of it.

Matthew:out

[mar]

Hard to say, looks ok to me. What about makemove.h? Are you sure you don't anything weird there?

[stegemma]

Try renaming Valid to IsValid... maybe gcc get confused from similar names somewhere?

PS: or maybe try:

struct Position * MakeMove(struct Position * Pos, int Move)

[Rein Halbersma]

Can you create a self-contained example + compiler options (I'm assuming this is C-code, not C++?) that demonstrates the problem? Something that can be copy-pasted into an online compiler.

[hgm]

Are you sure that gcc sees this definition of Position? If BOARD is already defined elsewhere it would skip the whole thing.

Add an intentional syntax error in the definition of Position, to test if the compiler processes this code.

[ZirconiumX]

Code: Select all

typedef struct {
	int Board[128];
	int WhiteToMove;
	int Castling; // KQkq
	int EnPassant;
	int Halfmove;
	int Valid; // Here is what GCC does not see.
} Position;

static const int Black = 0;
static const int White = 1;

static const int Nothing = 0;

static const int WhitePawn = 1;
static const int WhiteKnight = 2;
static const int WhiteBishop = 3;
static const int WhiteRook = 4;
static const int WhiteQueen = 5;
static const int WhiteKing = 6;

static const int BlackPawn = 7;
static const int BlackKnight = 8;
static const int BlackBishop = 9;
static const int BlackRook = 10;
static const int BlackQueen = 11;
static const int BlackKing = 12;

int CastlingMask[128] = {
	11, 16, 16, 16,  3, 16, 16,  7, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
	14, 16, 16, 16, 12, 16, 16, 13, 16, 16, 16, 16, 16, 16, 16, 16
};

Position * MakeMove(Position * Pos, int Move)
{
	int from = Move & 0x7F;
	int dest = (Move >> 7) & 0x7F;
	int flag = Move >> 14;

   // Off the board testing in case my move generator has a bug
	if (from & 0x88 || dest & 0x88)
		Pos->Valid = 0;

	Pos->Board[dest] = Pos->Board[from];
	Pos->Board[from] = Nothing;

	Pos->WhiteToMove ^= 1;

   // Castling, idea borrowed from DanaSah
	Pos->Castling &= CastlingMask[from] & CastlingMask[dest];

   // Promotion
	if (flag) {
		if (flag == 1)
			Pos->Board[dest] = (Pos->Board[dest] == WhitePawn) ? WhiteQueen : BlackQueen;
		if (flag == 2)
			Pos->Board[dest] = (Pos->Board[dest] == WhitePawn) ? WhiteRook : BlackRook;
		if (flag == 3)
			Pos->Board[dest] = (Pos->Board[dest] == WhitePawn) ? WhiteBishop : BlackBishop;
		if (flag == 4)
			Pos->Board[dest] = (Pos->Board[dest] == WhitePawn) ? WhiteKnight : BlackKnight;
	}

   // En Passant square, not yet tested
	if (Pos->Board[dest] == WhitePawn && dest - from == 32)
		Pos->EnPassant = from + 16;
	else if (Pos->Board[dest] == BlackPawn && from - dest == 32)
		Pos->EnPassant = dest + 16;
	else Pos->EnPassant = 255; // Since we're using a 128 element board, 255 is obviously off the board

	return Pos;
}

int main()
{
    printf("it works\n");
    return 0;
}

Manually preprocessed source. Hope this reproduces the problem.

makemove.h simply contains the function prototype for MakeMove().

No real compiler options at all - I just do gcc -o program *.c in the source code directory. No point optimising code that could be broken.

Matthew:out

[Rein Halbersma]

works for gcc 4.9.0 http://coliru.stacked-crooked.com/a/d85cebb9404bb824

[ZirconiumX]

Are you sure that gcc sees this definition of Position? If BOARD is already defined elsewhere it would skip the whole thing.

Add an intentional syntax error in the definition of Position, to test if the compiler processes this code.

Syntax error both before and after the member Valid is picked up just fine.

Test case I posted works fine for me too. Hmm.

Matthew:out

[ZirconiumX]

Ah, fixed it. GCC was using an out of date compiled header for board.h.

You'd think it would automatically regenerate it...

Matthew:out

[Rein Halbersma]

Pro tip: http://sscce.org/ Just going through these steps yourself before posting, will solve most problems on their own because you will identify the problem.