visual c++ 8 (.net 2005) has unresolved external symbol errors

[andrey.vul]

The error is LNK2001: unresolved external symbol "protected: static
bool solver<typename , typename, int, int, int, int,
int>::solution" (<vc++ mangled name>)
Code (sudoku.cpp):
// Sudoku.cpp : Defines the entry point for the console application.
//
#include <iostream>
#include <vector>
#include <stdexcept>
#include <cstdlib>
#include <cmath>
#include <cstring>

#ifdef _MSC_VER
#define inline __inline
#endif

typedef unsigned __int8 u8;
typedef signed __int8 s8;
typedef unsigned __int16 u16;
typedef signed __int16 s16;
typedef unsigned __int32 u32;
typedef signed __int32 s32;
typedef signed __int64 u64;
typedef signed __int64 s64;

#define nullptr(T) (T *)0

#define check_calloc(pt r, ptrname, type, n, if_fail, if_fail_msg) \
if (ptr == nullptr(type)) {\
cerr << "calloc could not allocate " << ptrname << " [n=" << n <<
"], " << if_fail_msg; \
if_fail; \
}

//safety check: at least 1 _N must be defined
#if (!(defined _4) && !(defined _9) && !(defined _16) \
&& !(defined _25) && !(defined _36) && !(defined _49) && !(defined
_64))
#error "No _N(s) declared!!!"
#endif

using namespace std;

template <typename T, int nstruct sumOfBits {
static const T value = (T)((1 << (n - 1)) + sumOfBits<T, n -
1>::value);
};
template<typena me Tstruct sumOfBits<T, 0{
static const T value = (T)0;
};

template <typename T>
class array {
public:
size_t length;
array(size_t _length) {
data = new T[_length];
length = _length;
}
T& operator[](unsigned int n) {
if ((size_t)n >= length) {
clog << "Array index out of range (n=" << n << ", length=" <<
length << "\"\n";
throw out_of_range("A rray index out of range");
}
return data[n];
}
T& elem(unsigned int n) {
return data[n];
}
~array() { delete[] data; }
private:
T* data;
};

//templates: flexible hardcoding :P
template <typename cell_t = u16, typename pos_t = u8,
unsigned int width = 9, unsigned int width_rt = 3, int width_sq = 81,
cell_t val_mask = sumOfBits<u16, 9>::value,
unsigned int zb_len = 11>
class solver {
public:
solver() {
cells = (cell_t *)calloc(width_ sq, sizeof(cell_t)) ;
zeroBit = (char *)calloc(zb_len , 1);
}
//garbage collection
~solver() {
free(cells);
cells = (cell_t *)0;
free(zeroBit);
zeroBit = (char *)0;
}
static u8 *solve(u8 *board) {
solver *s = encode(board);
solver *s_copy = s;
u8 *sol = nullptr(u8);
solution = false;
s = s->search();
if (solution) {
sol = s->decode();
delete s;
} else
delete s_copy;
return sol;
}
protected:
//data
cell_t *cells;
//0th bit
char *zeroBit;
//is the puzzle solved
static bool solution;
//copy current solver
solver *duplicate(void ) {
solver *dest = new solver();
pos_t i;
for (i = 0; i < width_sq; i++) {
dest->cells[i] = cells[i];
dest->zeroBit[i] = zeroBit[i];
}
return dest;
}
//check zeroBit
inline bool checkBit(pos_t i, char bit) {
u8 _byte = (u8)floor((i + 1) / 8.0);
return ((zeroBit[_byte] & (1 << (i % 8))) == bit) ? true : false;
}
//find most constrained position
pos_t constrained(voi d) {
u8 max = sumOfBits<u8, 7>::value;
pos_t maxp = (pos_t)max, i;
u8 j, v;

for (i = 0; i < width_sq; ++i) {
if (checkBit(i, 0)) {
v = 0;
for (j = 0; j < width; ++j)
if (((1 << j) & cells[i]) != 0)
++v;
if (v >= max || max >= sumOfBits<u8, 7>::value) {
max = v;
maxp = i;
}
}
}
return maxp;
}
//get all available options for value val
array<u8*option s(cell_t val) {
vector<u8cc(0);
array<u8*arr;
u8 i;
//find and add avialbale numbers
for (i = 0; i < width; ++i)
if (((1 << i) & val) == 0)
cc.push_back(i + 1);
arr = new array<u8>(cc.si ze());
for (i = 0; i < arr->length; i++)
arr->elem(i) = cc[i];
return arr;
}
//set value val in position pos, NOT-masking the other positions in
the group
void set(pos_t pos, u8 val) {
//column
u8 x = pos % width;
//row
u8 y = (u8)floor((pos * 1.0) / width);
//zone column, row
u8 zx = (u8)floor((x * 1.0) / width_rt) * width_rt;
u8 zy = (u8)floor((y * 1.0) / width_rt) * width_rt;
//value bit
cell_t add = 1 << ((cell_t)val - 1);
u8 k;
//NOT-mask the other positions in the group
for (k = 0; k < width; ++k) {
//mask column
cells[x + k * width] |= add;
//mask row
cells[k + y * width] |= add;
//mask zone
cells[zx + (k % width_rt) + width * (zy + (u8)floor((k * 1.0) /
width_rt))] |= add;
}
//unmask pos
cells[pos] = val_mask - add;
}
//sanity check
inline bool okay(void) {
pos_t i;
for (i = 0; i < width_sq; ++i)
if (((cells[i] & val_mask) == val_mask) && checkBit(i, 0))
return false;
return true;
}
//check if solved
inline bool solved(void) {
pos_t i;
for (i = 0; i < width_sq; ++i) {
if (checkBit(i, 0))
return false;
}
return true;
}
//search for solutions, return pointer to solution or null pointer
solver *search(void) {
pos_t p;
array<u8*l;
u8 i;
solver *ns;
solver *ns_backup; //avoid memory leaks by backing up pointer
while (okay()) {
if (solved()) {
solution = true;
return this;
}
//start solving from most constrained position
p = constrained();
//no solution
if (p < 0)
return nullptr(solver) ;
//get all the available options for cell p
l = options(cells[p]);
//no solution
if (l->length < 1)
return nullptr(solver) ;
//try each option in cell p by recursing ourselves
//(i.e., (...(ns = this) ... = this))
for (i = 0; i < l->length; ++i) {
//recurse
ns = duplicate();
ns->set(p, l->elem(i));
ns_backup = ns; //avoid memory leaks
ns = ns->search();
//solution found, recurse back up
if (ns != nullptr(solver) )
return ns;
else //solution not found, deallocate ns using backup
delete ns_backup;
}
//try first option
set(p, l->elem(0));
}
//failed sanity check
return nullptr(solver) ;
}
//decode bitmask solution to numerical solution
u8 *decode(void) {
u8 *arr = (u8 *)calloc(width_ sq, sizeof(u8));
if (arr == nullptr(u8))
return arr;
pos_t i;
u8 j;
for (i = 0; i < width_sq; ++i)
for (j = 0; j < width; ++j)
if (((cells[i] | (cell_t)(1 << j)) == val_mask) && checkBit(i, 1))
{
arr[i] = j + (width < 10 ? 1 : 0);
break;
}
return arr;
}
static solver *encode(u8 *arr) {
solver *a = new solver();
pos_t i;
for (i = 0; i < width_sq; ++i) {
/* MAKE SURE that the number is between 1 and 9, inclusive so that
the
* solver does NOT mask 0 because that would break function isOK()
and
* hence prevent the solver from reaching a solution.
*/
if (width < 10) {
if (arr[i] >= 1 && arr[i] <= width)
a->set(i, arr[i]);
} else {
if (arr[i] >= 0 && arr[i] < width)
a->set(i + 1, arr[i]);
}
}
return a;
}
solver<cell_t, pos_t, width, width_rt, width_sq, val_mask, zb_len>::
};
//pase sIng to array
u8 *parse (char *str, unsigned __int8 base) {
u8 i;
u16 b2;
b2 = base * base;
u8 *arr = (u8 *)calloc(b2, 1);
if (arr == nullptr(u8))
return nullptr(u8);
for (i = 0; i < b2; i++) {
if (str[i] >= 0x30 && str[i] <= 0x39) //'0'-'9'
arr[i] = str[i] - 0x30;
else if (base >= 11) { //'a'-'z'
if (str[i] >= 0x61 && str[i] <= 0x7a)
arr[i] = str[i] - 0x57;
}
else if (base >= 37) { //'A'-'Z'
if (str[i] >= 0x41 && str[i] <= 0x5a)
arr[i] = str[i] - 0x1d;
}
else if (base >= 62) { //','-'.'
if (str[i] == 0x2c || str[i] == 0x2e)
arr[i] = (str[i] == 0x2c ? 62 : 63);
}
else
arr[i] = 1 << 7;
}
return arr;
}
//create sIng from array
char *arr_str(const u8 *arr, u16 len) {
char *str = (char *)calloc(len, 1);
u16 i;
if (str == nullptr(char))
return nullptr(char);
for (i = 0; i < len; i++) {
if (arr[i] < 10) str[i] = arr[i] + 0x30; //0-9
else if (arr[i] < 37) str[i] = arr[i] + 0x57; //a-z
else if (arr[i] < 62) str[i] = arr[i] + 0x1d; //A-Z
else if (arr[i] == 62) str[i] = 0x2c; //,
else if (arr[i] == 63) str[i] = 0x2e; //.
else str[i] = 0x3f; //?
}
return str;
}

int main(int argc, char *argv[]) {
u8 doku;
u8 *arr;
u8 *sol;
char *sIn = nullptr(char);
if (argc == 3)
doku = (strncmp(argv[1], "16", 3) == 0) ? 16
: (strncmp(argv[1], "25", 3) == 0) ? 25
: (strncmp(argv[1], "36", 3) == 0) ? 36
: (strncmp(argv[1], "4", 2) == 0) ? 4
: (strncmp(argv[1], "49", 3) == 0) ? 49
: (strncmp(argv[1], "64", 3) == 0) ? 64
: (strncmp(argv[1], "9", 2) == 0) ? 9
: 0;
else
doku = 9; //sudoku (9)
switch (argc) {
case 2: //puzzle from argv[1]
#if ((defined _4) && !(defined _9) && !(defined _16) \
&& !(defined _25) && !(defined _36) && !(defined _49) && !(defined
_64))
arr = parse(argv[1], 16);
check_calloc(ar r, "arr", u8, 16, goto error, "exiting...\n") ;
goto doku4;
#endif //(_4)
#ifdef _9
arr = parse(argv[1], 81);
check_calloc(ar r, "arr", u8, 81, goto error, "exiting...\n") ;
goto doku9;
#endif //_9
#if (!(defined _4) && !(defined _9) && (defined _16) \
&& !(defined _25) && !(defined _36) && !(defined _49) && !(defined
_64))
arr = parse(argv[1], 256);
check_calloc(ar r, "arr", u8, 256, goto error, "exiting...\n") ;
goto doku16;
#endif //(_16)
#if (!(defined _4) && !(defined _9) && !(defined _16) \
&& (defined _25) && !(defined _36) && !(defined _49) && !(defined
_64))
arr = parse(argv[1], 625);
check_calloc(ar r, "arr", u8, 625, goto error, "exiting...\n") ;
goto doku25;
#endif //(_25)
#if (!(defined _4) && !(defined _9) && !(defined _16) \
&& !(defined _25) && (defined _36) && !(defined _49) && !(defined
_64))
arr = parse(argv[1], 1296);
check_calloc(ar r, "arr", u8, 1296, goto error, "exiting...\n") ;
goto doku36;
#endif //(_36)
#if (!(defined _4) && !(defined _9) && !(defined _16) \
&& !(defined _25) && !(defined _36) && (defined _49) && !(defined
_64))
arr = parse(argv[1], 2401);
check_calloc(ar r, "arr", u8, 2401, goto error, "exiting...\n") ;
goto doku49;
#endif //(_49)
#if (!(defined _4) && !(defined _9) && !(defined _16) \
&& !(defined _25) && !(defined _36) && !(defined _49) && (defined
_64))
arr = parse(argv[1], 4096);
check_calloc(ar r, "arr", u8, 4096, goto error, "exiting...\n") ;
goto doku64;
#endif //(_64)
case 3: //puzzle from argv[2]
switch (doku) {
#ifdef _4
case 4:
arr = parse(argv[2], 16);
check_calloc(ar r, "arr", u8, 16, goto error, "exiting...\n") ;
goto doku4;
#endif //_4
#ifdef _9
case 9:
arr = parse(argv[2], 81);
check_calloc(ar r, "arr", u8, 81, goto error, "exiting...\n") ;
goto doku9;
#endif //_9
#ifdef _16
case 16:
arr = parse(argv[2], 256);
check_calloc(ar r, "arr", u8, 256, goto error, "exiting...\n") ;
goto doku16;
#endif //_16
#ifdef _25
case 25:
arr = parse(argv[2], 625);
check_calloc(ar r, "arr", u8, 625, goto error, "exiting...\n") ;
goto doku25;
#endif //_25
#ifdef _36
case 36:
arr = parse(argv[2], 1296);
check_calloc(ar r, "arr", u8, 1296, goto error, "exiting...\n") ;
goto doku36;
#endif //_36
#ifdef _49
case 49:
arr = parse(argv[2], 2401);
check_calloc(ar r, "arr", u8, 2401, goto error, "exiting...\n") ;
goto doku49;
#endif //_49
#ifdef _64
case 64:
arr = parse(argv[2], 4096);
check_calloc(ar r, "arr", u8, 4096, goto error, "exiting...\n") ;
goto doku64;
#endif //_64
} //case 3 switch (doku)
case 1: //puzzle from stdin
switch (doku) {
#ifdef _4
case 4:
sIn = (char *)calloc(17, 1);
check_calloc(sI n, "sIn", char, 17, goto error, "exiting...\n") ;
cin >sIn;
arr = parse(sIn, 16);
check_calloc(ar r, "arr", u8, 16, goto error, "exiting...\n") ;
goto doku4;
#endif //_4
#ifdef _9
case 9:
sIn = (char *)calloc(82, 1);
check_calloc(sI n, "sIn", char, 82, goto error, "exiting...\n") ;
cin >sIn;
arr = parse(sIn, 81);
check_calloc(ar r, "arr", u8, 81, goto error, "exiting...\n") ;
goto doku9;
#endif //_9
#ifdef _16
case 16:
sIn = (char *)calloc(257, 1);
check_calloc(sI n, "sIn", char, 257, goto error, "exiting...\n") ;
cin >sIn;
arr = parse(sIn, 256);
check_calloc(ar r, "arr", u8, 256, goto error, "exiting...\n") ;
goto doku16;
#endif //_16
#ifdef _25
case 25:
sIn = (char *)calloc(626, 1);
check_calloc(sI n, "sIn", char, 626, goto error, "exiting...\n") ;
cin >sIn;
arr = parse(sIn, 625);
check_calloc(ar r, "arr", u8, 625, goto error, "exiting...\n") ;
goto doku25;
#endif //_25
#ifdef _36
case 36:
sIn = (char *)calloc(1297, 1);
check_calloc(sI n, "sIn", char, 1297, goto error, "exiting...\n") ;
cin >sIn;
arr = parse(sIn, 1296);
check_calloc(ar r, "arr", u8, 1296, goto error, "exiting...\n") ;
goto doku36;
#endif //_36
#ifdef _49
case 49:
sIn = (char *)calloc(2402, 1);
check_calloc(sI n, "sIn", char, 2402, goto error, "exiting...\n") ;
cin >sIn;
arr = parse(sIn, 2401);
check_calloc(ar r, "arr", u8, 2401, goto error, "exiting...\n") ;
goto doku49;
#endif //_49
#ifdef _64
case 64:
sIn = (char *)calloc(4097, 1);
check_calloc(sI n, "sIn", char, 4097, goto error, "exiting...\n") ;
cin >sIn;
arr = parse(sIn, 4096);
check_calloc(ar r, "arr", u8, 4096, goto error, "exiting...\n") ;
goto doku64;
#endif //_64
} //case 1 switch (doku)
} //switch(argc)

#ifdef _4
doku4:
sol = solver<u8, u8, 4, 2, 8, sumOfBits<u8, 4>::value,
1>::solve(arr) ;
if (sol == nullptr(u8))
goto no_solution_fou nd;
else
goto solution_found;
#endif //_4
#ifdef _9
doku9:
sol = solver<u16, u8, 9, 3, 81, sumOfBits<u16, 9>::value,
11>::solve(arr) ;
if (sol == nullptr(u8))
goto no_solution_fou nd;
else
goto solution_found;
#endif //_9
#ifdef _16
doku16:
sol = solver<u16, u8, 16, 4, 256, sumOfBits<u16, 16>::value,
32>::solve(arr) ;
if (sol == nullptr(u8))
goto no_solution_fou nd;
else
goto solution_found;
#endif //_16
#ifdef _25
doku25:
sol = solver<u32, u16, 25, 5, 625, sumOfBits<u32, 25>::value,
79>::solve(arr) ;
if (sol == nullptr(u8))
goto no_solution_fou nd;
else
goto solution_found;
#endif //_25
#ifdef _36
doku36:
sol = solver<u64, u16, 36, 6, 1296, sumOfBits<u64, 36>::value,
162>::solve(arr );
if (sol == nullptr(u8))
goto no_solution_fou nd;
else
goto solution_found;
#endif //_36
#ifdef _49
doku49:
sol = solver<u64, u16, 49, 7, 2401, sumOfBits<u64, 49>::value,
301>::solve(arr );
if (sol == nullptr(u8))
goto no_solution_fou nd;
else
goto solution_found;
#endif //_49
#ifdef _64
doku64:
sol = solver<u64, u16, 64, 8, 4096, sumOfBits<u64, 64>::value,
512>::solve(arr );
if (sol == nullptr(u8))
goto no_solution_fou nd;
else
goto solution_found;
#endif //_64
no_solution_fou nd:
cout << "No solution found for puzzle " << (argc == 3 ? argv[2] :
(sIn != nullptr(char)) ? sIn : argv[1]) << endl;
goto done;
solution_found:
cout << "Solution for puzzle " << (argc == 3 ? argv[2] : (sIn !=
nullptr(char)) ? sIn : argv[1])
<< " is " << arr_str(sol, (u16)strlen((sI n != nullptr(char)) ? sIn :
argv[1])) << endl;
goto done;
error:
return 1;
done:
return 0;
}

Compile with options -D_4 -D_9 -D_16 -D_25 -D_36 -D_49 -D_64
Any (elegant?) way to fix the error (if you can use diif -Naur fromat,
that would be very nice)?

[=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?=]

On 2007-09-26 03:39, an********@gmai l.com wrote:

The error is LNK2001: unresolved external symbol "protected: static
bool solver<typename , typename, int, int, int, int,
int>::solution" (<vc++ mangled name>)

Do not know if it matters but the solver class takes unsigned ints as
template parameters, not ints. Sorry, cannot help you more than that,
too much macro magic for me.

--
Erik Wikström

[andrey.vul]

On 2007-09-26 03:39, an********@gmai l.com wrote:

The error is LNK2001: unresolved external symbol "protected: static
bool solver<cell_t, pos_t, width, width_sq, width_rt, val_mask,
zb_len>::soluti on" (<vc++ mangled name>)

The problem is that VC++ externs the variable, as seen from this line
of asm output:
EXTRN ?solution@?$sol ver@_KG$0EA@$07 $0BAAA@$0?0$0CA A@@@1_NA:BYTE ;
solver<cell_t, pos_t, width, width_sq, width_rt, val_mask,
zb_len>::soluti on

Any way to declare the variable or rework the class to fix this issue
(see first post for original code)?

[Pete Becker]

On 2007-09-26 13:13:24 -0400, an********@gmai l.com said:

>

>On 2007-09-26 03:39, an********@gmai l.com wrote:

>>The error is LNK2001: unresolved external symbol "protected: static
bool solver<cell_t, pos_t, width, width_sq, width_rt, val_mask,
zb_len>::solu tion" (<vc++ mangled name>)

The problem is that VC++ externs the variable, as seen from this line
of asm output:
EXTRN ?solution@?$sol ver@_KG$0EA@$07 $0BAAA@$0?0$0CA A@@@1_NA:BYTE ;
solver<cell_t, pos_t, width, width_sq, width_rt, val_mask,
zb_len>::soluti on

Any way to declare the variable or rework the class to fix this issue
(see first post for original code)?

No, thanks. That was way too much code for such a simple problem. Do
the work to eliminate things that don't contribute to the error. Then
add a definition for the missing object.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)

[=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?=]

On 2007-09-26 03:39, an********@gmai l.com wrote:

static solver *encode(u8 *arr) {
solver *a = new solver();
pos_t i;
for (i = 0; i < width_sq; ++i) {
/* MAKE SURE that the number is between 1 and 9, inclusive so that
the
* solver does NOT mask 0 because that would break function isOK()
and
* hence prevent the solver from reaching a solution.
*/
if (width < 10) {
if (arr[i] >= 1 && arr[i] <= width)
a->set(i, arr[i]);
} else {
if (arr[i] >= 0 && arr[i] < width)
a->set(i + 1, arr[i]);
}
}
return a;
}
solver<cell_t, pos_t, width, width_rt, width_sq, val_mask, zb_len>::
};

I took a new look at the code, and the line above is where my compiler
gave up, which is no surprise to me. When posting code that gives you
errors, make sure that it is exactly the same as the one that gave the
error. Also, please replace tabs with a few spaces (2-4 will do) since
it will reduce the number of broken lines and increase the readability.

--
Erik Wikström

[andrey.vul]

On Sep 26, 1:54 pm, Erik Wikström <Erik-wikst...@telia. comwrote:

On 2007-09-26 03:39, andrey....@gmai l.com wrote:

static solver *encode(u8 *arr) {
solver *a = new solver();
pos_t i;
for (i = 0; i < width_sq; ++i) {
/* MAKE SURE that the number is between 1 and 9, inclusive so that
the
* solver does NOT mask 0 because that wouldbreak function isOK()
and
* hence prevent the solver from reaching a solution.
*/
if (width < 10) {
if (arr[i] >= 1 && arr[i] <= width)
a->set(i, arr[i]);
} else {
if (arr[i] >= 0 && arr[i] < width)
a->set(i + 1, arr[i]);
}
}
return a;
}
solver<cell_t, pos_t, width, width_rt, width_sq, val_mask, zb_len>::

That was a typo line

};

I took a new look at the code, and the line above is where my compiler
gave up, which is no surprise to me. When posting code that gives you
errors, make sure that it is exactly the same as the one that gave the
error. Also, please replace tabs with a few spaces (2-4 will do) since
it will reduce the number of broken lines and increase the readability.

--
Erik Wikström

The condensed class (with error-causing code) is:
template <typename cell_t = u16, typename pos_t = u8,
unsigned int width = 9, unsigned int width_rt = 3, int width_sq =
81,
cell_t val_mask = sumOfBits<u16, 9>::value, unsigned int zb_len =
11>
class solver {
public:
static unsigned char *solve (unsigned char *board) {
...
solution = false;
s = s->search();
if (solution) {
...
}
...
}
protected:
static bool solution;
...
solver *search(void) {
...
while (...) {
if (...) {
solution = true;
return this;
}
...
}
}
};

.... refers to code that the error does not apply to

[Victor Bazarov]

an********@gmai l.com wrote:

On Sep 26, 1:54 pm, Erik Wikström <Erik-wikst...@telia. comwrote:

>On 2007-09-26 03:39, andrey....@gmai l.com wrote:

>> static solver *encode(u8 *arr) {
solver *a = new solver();
pos_t i;
for (i = 0; i < width_sq; ++i) {
/* MAKE SURE that the number is between
1 and 9, inclusive so that the
* solver does NOT mask 0 because that
would break function isOK() and
* hence prevent the solver from
reaching a solution. */
if (width < 10) {
if (arr[i] >= 1 && arr[i] <=
width) a->set(i, arr[i]);
} else {
if (arr[i] >= 0 && arr[i] <
width) a->set(i + 1,
arr[i]); }
}
return a;
}
solver<cell_t, pos_t, width, width_rt, width_sq, val_mask,
zb_len>::

That was a typo line

>>};

I took a new look at the code, and the line above is where my
compiler gave up, which is no surprise to me. When posting code that
gives you errors, make sure that it is exactly the same as the one

^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^

>that gave the error.

^^^^^^^^^^^^^^^ ^^^^^

>Also, please replace tabs with a few spaces
(2-4 will do) since it will reduce the number of broken lines and
increase the readability.

--
Erik Wikström

The condensed class (with error-causing code) is:
template <typename cell_t = u16, typename pos_t = u8,
unsigned int width = 9, unsigned int width_rt = 3, int width_sq =
81,
cell_t val_mask = sumOfBits<u16, 9>::value, unsigned int zb_len =
11>
class solver {
public:
static unsigned char *solve (unsigned char *board) {
...
solution = false;
s = s->search();
if (solution) {
...
}
...
}
protected:
static bool solution;
...
solver *search(void) {
...
while (...) {
if (...) {
solution = true;
return this;
}
...
}
}
};

... refers to code that the error does not apply to

Do you by any chance NOT understand the meaning of the words I've
highlighted above in Erik's message? Read the FAQ 5.8 (and the rest
of section 5) before posting your reply, please.

V
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