Why sscanf crashes when adding more variables? - pascal

Question

I have a string with a word at the begining (that I want to ignore) and then some numbers that I want to store in an array. Not all of them, just some.
I use sscanf like this
var
x: integer;
y: array[0..19] of integer;
s: pchar;
begin
...
sscanf(dataline, "%s %d %d %d %d %d %d %d %d %d %d %d",
[s, #x, #y[0], #y[1], #y[2], #y[3], #y[4],
#y[5], #y[6], #y[7], #y[8], #y[9]]);
...
end;
and it's ok. But if I want to read just one more
var
x: integer;
y: array[0..19] of integer;
s: pchar;
begin
...
sscanf(dataline, "%s %d %d %d %d %d %d %d %d %d %d %d %d",
[s, #x, #y[0], #y[1], #y[2], #y[3], #y[4],
#y[5], #y[6], #y[7], #y[8], #y[9], #y[10]]);
...
end;
then I get a runtime error: "The project myproject has thrown an exception of class 'External: SIGSEGV'. at address 82E37E1".
Any ideas of what can go wrong? Thank you very much.
I'm using lazarus 1.2.4 with fpc 2.6.4 in Linux Mint 17.1 32bits.
EDIT: As Abelisto suggested, the issue was about s, I changed it from PChar to String and initialized it with some spaces and everything works fine. The code reads the lines in a TMemo to get the data, then makes a table (in a TListView) adding the values and then the minimum, average and maximum value. Note that 1023 is the maximum value possible.
procedure TfMain.bGetDataClick(Sender: TObject);
const
dataPoints = 20;
var
it: TListItem;
n, i, x, avg, min, max: integer;
y: array[0 .. dataPoints - 1] of integer;
dataLine: string;
s: string = ' ';
begin
datalist.BeginUpdate;
datalist.Clear;
n := -1;
while n < cSerIn.Lines.Count do
begin
Inc(n);
dataLine := cSerIn.Lines[n];
sscanf(dataLine, '%s %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d',
[#s, #x, #y[0], #y[1], #y[2], #y[3], #y[4],
#y[5], #y[6], #y[7], #y[8], #y[9],
#y[10], #y[11], #y[12], #y[13], #y[14],
#y[15], #y[16], #y[17], #y[18], #y[19]]);
it := dataList.Items.Add;
it.Caption := IntToStr(x);
avg := 0;
min := 1023;
max := 0;
for i := 0 to dataPoints-1 do
begin
it.SubItems.Add(IntToStr(y[i]));
avg += y[i];
if y[i] < min then min := y[i];
if y[i] > max then max := y[i];
end;
avg := avg div dataPoints;
it.SubItems.Insert(0, IntToStr(max));
it.SubItems.Insert(0, IntToStr(avg));
it.SubItems.Insert(0, IntToStr(min));
end;
datalist.EndUpdate;
end;
Also I realized my fpc version is 2.6.4, not 2.6.0. Thanks everyone for the help!

Answer 1

program project1;
uses
sysutils;
const
CArrCnt = 19;
var
x: integer;
y: array[0..CArrCnt] of integer;
s: string; // changes here
dataline: string;
i: Integer;
begin
dataline := 'aaa 123 0 1 2 3 4 5 6 7 8 9 10 11';
s := ' '; // changes here
sscanf(dataline, '%s %d %d %d %d %d %d %d %d %d %d %d %d %d',
[#s, #x, #y[0], #y[1], #y[2], #y[3], #y[4], #y[5],
#y[6], #y[7], #y[8], #y[9], #y[10], #y[11]]);
WriteLn(s);
Writeln(x);
for i := 0 to CArrCnt do
WriteLn(y[i]);
ReadLn;
end.
works fine.
You have to show more of the program code. For example we are not know is memory for s: pchar; was allocated.
BTW: Win7, FPC 3.1.1 32 bit.