Re: yet another segfault - array out of bound is not caught by try catch
Double check in your dub.json file and see if you haven't changed your buildoptions DEBUG: it's caught: https://run.dlang.io/is/F8HkD8 RELEASE: segfault as expected: https://run.dlang.io/is/oLU2M3 And make sure to use latest version of ldc
Re: yet another segfault - array out of bound is not caught by try catch
On Friday, 17 September 2021 at 11:10:33 UTC, seany wrote:
Compile with `dub build --compiler=ldc2 `. this should enable
array bound checking options.
By default, yes. run `dub -v build --compiler=ldc2` to see the
exact commands that dub runs.
But should it not be caught by range error ?
Based on what you've said, yes it should.
If I do `print l`in gdb, i find :
$1 = {length = 0, ptr = 0x0}
With `print l[0]` i get: `Attempt to take address of value not
located in memory.`.
i.e., a segfault. null (or 0x0 (or 0)) isn't part of the memory
addresses your program is allowed to access, so memory protection
prevents the attempt to access it.
What absolute rookie mistake am I committing?
From this it doesn't sound like you are committing one, but if
you're wanting bounds checking to be a normal part of program
logic, and not something that only ever happens due to a
programmer's error, then I think you're cutting against the grain
of the language, where
- bounds checking is easily removed from all but @safe functions
with normal flags
- flags exist to remove it from @safe functions also
- the *Error family of exceptions, including RangeError are not
intended to be catchable
- raising and immediately catching an exception like this is
slower and more verbose than an explicit test.
Rather than returning an empty array on an error and expecting a
caller to catch RangeError, you could throw a normal exception on
error, and then you have tools like `std.exception.ifThrown` to
make dealing with that exception nicer.
Re: yet another segfault - array out of bound is not caught by try catch
On Friday, 17 September 2021 at 11:10:33 UTC, seany wrote:
I have now this function, as a private member in a Class :
} catch (RangeError er) {
I can't remember if you can catch an index OOB error but try
`catch (Throwable er)` will work if it is catchable at all and
you can figure out what kind of Error you have by printing its
name.
"Attempt to take address of value not located in memory" ? I
am not even calling / accessing a pointer. I am trying to
extract a value outside an array bound.
`Type[]` arrays in D are effectively struct {size_t length; Type*
ptr; } under the hood. Your problem is the array has no elements
which is why trying to extract a value outside an array bound is
an irrecoverable error.
with the bound checking operation in place, would the bound
error be triggered before the attempt to take unavailable
address error has a chance to trigger?
with a null array of zero length `arr`, `arr[0]` with bounds
check enabled will fail the bounds check before it tries to
dereference the pointer. if you try `arr.ptr[0]` to bypass the
bounds checking (which is a very bad idea!) you will then try to
load from an invalid memory address and crash.
yet another segfault - array out of bound is not caught by try catch
I have now this function, as a private member in a Class :
double calculate_lineLength( int i) {
field.rawData [] * rd; // ignore
the details, this works;
rd = cast (field.rawData [] *) dataSet; // ignore
the details, this works;
auto l = this.allLines[i]; // this is
defined as
// int [][]
allLines =
//
new int [][] (0,0)
// in case
of failure, this is empty
double r = 0;
try {
writeln("l ", l);// prints []
writeln("i ", i);// prints i,
in this case, i is set to 0
writeln(l.length); // prints 0
writeln("l0 ", l[0]);// segfault
- i want it to be caught
write("will print");
writeln("rd", (*rd));
write("will not print...");
auto p0 = (*rd)[l[0]];
auto p1 = (*rd)[l[1]];
r = calculate_geoDistance_vincenty(p0.lat,p1.lat,
p0.lon, p1.lon);
} catch (RangeError er) {
writeln("range error");
}
return r;
}
Compile with `dub build --compiler=ldc2 `. this should enable
array bound checking options.
I am debugging with gdb :
`gdb ./myprogram`
Then, in gdb console :
`run arg1 arg2 `
Result is :
91753
91754
91755
91756
[New Thread 0x77560640 (LWP 45344)]
[New Thread 0x7fffe640 (LWP 45345)]
[New Thread 0x76d5f640 (LWP 45346)]
[New Thread 0x7655e640 (LWP 45347)]
[New Thread 0x75d5d640 (LWP 45348)]
[New Thread 0x7555c640 (LWP 45349)]
[New Thread 0x74d5b640 (LWP 45350)]
[New Thread 0x7fffef7fe640 (LWP 45351)]
[New Thread 0x7fffeeffd640 (LWP 45352)]
[New Thread 0x7fffee7fc640 (LWP 45353)]
[New Thread 0x7fffedffb640 (LWP 45354)]
[New Thread 0x7fffed7fa640 (LWP 45355)]
[New Thread 0x7fffecff9640 (LWP 45356)]
[New Thread 0x7fffb640 (LWP 45357)]
[New Thread 0x7fffbf7fe640 (LWP 45358)]
[New Thread 0x7fffbeffd640 (LWP 45359)]
[New Thread 0x7fffbe7fc640 (LWP 45360)]
[New Thread 0x7fffbdffb640 (LWP 45361)]
[New Thread 0x7fffbd7fa640 (LWP 45362)]
getting LINES done
alllines: []
l []
i 0
0
Thread 1 "myprogram" received signal SIGSEGV,
Segmentation fault.
_D14analysisEngine9geoEngine20calculate_lineLengthMFiZd
(this=, i=0) at source/analysisEngine.d:15526
15526
writeln("l0 ", l[0]);
So, to see what is going on, i use the command `bt`:
#0
_D14analysisEngine9geoEngine20calculate_lineLengthMFiZd
(this=, i=0) at source/analysisEngine.d:15526
#1 0x555dba40 in
_D14analysisEngine9geoEngine13add_turnLinesMFZv (this=out>) at source/analysisEngine.d:7387
#2 0x555e375a in
_D14analysisEngine9geoEngine15analyze_tillageMFZv
(this=0x7756a000) at source/analysisEngine.d:5329
#3 0x5560d082 in _Dmain (args=...) at
source/AI.d:123
Okey, I know where to look for : it's the line asking for
`writeln("l0 ", l[0]);`.
But should it not be caught by range error ? If I do `print
l`in gdb, i find :
$1 = {length = 0, ptr = 0x0}
With `print l[0]` i get: `Attempt to take address of value not
located in memory.`. I believe the array printing syntax is
valid; see
[here](https://phoenix.goucher.edu/~kelliher/cs23/gdb.html).
What absolute rookie mistake am I committing? What does it mean :
"Attempt to take address of value not located in memory" ? I am
not even calling / accessing a pointer. I am trying to extract a
value outside an array bound.
I imagine they all have their addresses. But with the bound
checking operation in place, would the bound error be triggered
before the attempt to take unavailable address error has a chance
to trigger?
Thank you.
