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digitalmars.D.learn - Program exited with code -11 when calling

reply Anthony <anthoq88 gmail.com> writes:
I'm trying to convert this c function:

bson_t *bson_new_from_json (const uint8_t *data, ssize_t len, 
bson_error_t *error);


Into a D function. This is my attempt:
extern(C) {
     struct bson_t;
     struct bson_error_t;

     bson_t* bson_new_from_json(const uint8_t* data, long len, 
bson_error_t* error);
}

However when I try it, for example:

auto str_utf8 = str.toUTF8();
bson_error_t error

auto bson = bson_new_from_json(cast(const uint8_t*)str_utf8.ptr, 
-1, &error);


I get a "Program exited with code -11" message.
Does anyone know what I'm doing wrong?

Thanks
Jun 30 2020
next sibling parent reply Cym13 <cpicard openmailbox.org> writes:
On Wednesday, 1 July 2020 at 05:04:28 UTC, Anthony wrote:

 I'm trying to convert this c function:

 bson_t *bson_new_from_json (const uint8_t *data, ssize_t len, 
 bson_error_t *error);


 Into a D function. This is my attempt:
 extern(C) {
     struct bson_t;
     struct bson_error_t;

     bson_t* bson_new_from_json(const uint8_t* data, long len, 
 bson_error_t* error);
 }

 However when I try it, for example:

 auto str_utf8 = str.toUTF8();
 bson_error_t error

 auto bson = bson_new_from_json(cast(const 
 uint8_t*)str_utf8.ptr, -1, &error);


 I get a "Program exited with code -11" message.
 Does anyone know what I'm doing wrong?

 Thanks


I don't know the exact function you are trying to use, but -11 
means "segmentation fault" on linux. This means that your program 
is trying to read or write a memory location that it is not 
supposed to. This typically happens during buffer overflows and 
similar memory corruption bugs.

One thing that jumps to me is the -1 in your call instead of the 
length. Without knowing the C function's implementation I would 
expect it to mean either "read before the array" which would be a 
buffer overflow or to have the special meaning of "deduce the 
string size yourself". In that last case I would expect 
bson_new_from_json to expect a NUL-terminated array, but I don't 
know if your UTF8 array is NUL-terminated.
Jun 30 2020
parent reply Anthony <anthoq88 gmail.com> writes:
On Wednesday, 1 July 2020 at 05:09:47 UTC, Cym13 wrote:

 On Wednesday, 1 July 2020 at 05:04:28 UTC, Anthony wrote:

 I'm trying to convert this c function:

 bson_t *bson_new_from_json (const uint8_t *data, ssize_t len, 
 bson_error_t *error);


 Into a D function. This is my attempt:
 extern(C) {
     struct bson_t;
     struct bson_error_t;

     bson_t* bson_new_from_json(const uint8_t* data, long len, 
 bson_error_t* error);
 }

 However when I try it, for example:

 auto str_utf8 = str.toUTF8();
 bson_error_t error

 auto bson = bson_new_from_json(cast(const 
 uint8_t*)str_utf8.ptr, -1, &error);


 I get a "Program exited with code -11" message.
 Does anyone know what I'm doing wrong?

 Thanks


 I don't know the exact function you are trying to use, but -11 
 means "segmentation fault" on linux. This means that your 
 program is trying to read or write a memory location that it is 
 not supposed to. This typically happens during buffer overflows 
 and similar memory corruption bugs.

 One thing that jumps to me is the -1 in your call instead of 
 the length. Without knowing the C function's implementation I 
 would expect it to mean either "read before the array" which 
 would be a buffer overflow or to have the special meaning of 
 "deduce the string size yourself". In that last case I would 
 expect bson_new_from_json to expect a NUL-terminated array, but 
 I don't know if your UTF8 array is NUL-terminated.



Thanks for getting back to me.

Yeah I figured it was a segmentation fault, however, I don't know 
exactly how to pinpoint where this is happening. I'm wondering if 
there's anything wrong with how I'm casting the data since 
everything is self contained (assuming bson_new_from_json is 
correct since it works using c directly).

void foo() {
     import std.utf;
     import core.stdc.stdint;

     auto str_utf8 = "{\"a\":1}";
     bson_error_t error;

     bson_new_from_json(cast(uint8_t*)str_utf8, 
(cast(uint8_t[])str_utf8).length, &error);
}



Re -1 in the call: Apparently it uses strlen() to deduce the 
size. However, I tried explicitly state the array length but had 
no luck.
Jun 30 2020
parent Kagamin <spam here.lot> writes:
bson_t* bson_new_from_json(in char* data, long len, bson_error_t* 
error);

string str_utf8 = "{\"a\":1}";
bson_error_t error;

auto bson = bson_new_from_json(str_utf8.ptr, str_utf8.length, 
&error);

You have a wrong declaration for bson_error_t too.
Jun 30 2020
prev sibling parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Wed, Jul 01, 2020 at 05:04:28AM +0000, Anthony via Digitalmars-d-learn wrote:
[...]

 auto str_utf8 = str.toUTF8();
 bson_error_t error
 
 auto bson = bson_new_from_json(cast(const uint8_t*)str_utf8.ptr, -1,
 &error);
 
 
 I get a "Program exited with code -11" message.
 Does anyone know what I'm doing wrong?


D strings are generally not null-terminated (except for literals).
Before passing them to a C function you need to add a trailing null. Try
using std.conv.toStringz instead of casting the pointer yourself.


T

-- 
A programming language should be a toolbox for the programmer to draw upon, not
a minefield of dangerous explosives that you have to very carefully avoid
touching in the wrong way.
Jun 30 2020
parent reply Anthony <anthoq88 gmail.com> writes:
On Wednesday, 1 July 2020 at 05:33:48 UTC, H. S. Teoh wrote:

 On Wed, Jul 01, 2020 at 05:04:28AM +0000, Anthony via 
 Digitalmars-d-learn wrote: [...]

 auto str_utf8 = str.toUTF8();
 bson_error_t error
 
 auto bson = bson_new_from_json(cast(const 
 uint8_t*)str_utf8.ptr, -1,
 &error);
 
 
 I get a "Program exited with code -11" message.
 Does anyone know what I'm doing wrong?


 D strings are generally not null-terminated (except for 
 literals). Before passing them to a C function you need to add 
 a trailing null. Try using std.conv.toStringz instead of 
 casting the pointer yourself.


 T


Thanks H. S. Teoh.
Hmm, still same result though.


     import std.string;

     auto str = toStringz("{\"a\":1}");

     bson_error_t error;

     bson_new_from_json(str, -1, &error);




     extern(C) {
         ...
         bson_t* bson_new_from_json(const char* data, long len, 
bson_error_t* error);
     }
Jun 30 2020
parent Anthony <anthoq88 gmail.com> writes:
On Wednesday, 1 July 2020 at 05:47:16 UTC, Anthony wrote:

 On Wednesday, 1 July 2020 at 05:33:48 UTC, H. S. Teoh wrote:

 On Wed, Jul 01, 2020 at 05:04:28AM +0000, Anthony via 
 Digitalmars-d-learn wrote: [...]

 auto str_utf8 = str.toUTF8();
 bson_error_t error
 
 auto bson = bson_new_from_json(cast(const 
 uint8_t*)str_utf8.ptr, -1,
 &error);
 
 
 I get a "Program exited with code -11" message.
 Does anyone know what I'm doing wrong?


 D strings are generally not null-terminated (except for 
 literals). Before passing them to a C function you need to add 
 a trailing null. Try using std.conv.toStringz instead of 
 casting the pointer yourself.


 T


 Thanks H. S. Teoh.
 Hmm, still same result though.


     import std.string;

     auto str = toStringz("{\"a\":1}");

     bson_error_t error;

     bson_new_from_json(str, -1, &error);




     extern(C) {
         ...
         bson_t* bson_new_from_json(const char* data, long len, 
 bson_error_t* error);
     }


Noob mistake:
I declared an array that should be of fixed size.

     struct bson_error_t {
         ....
         char[] message;
     };

Should be:

     struct bson_error_t {
         ....
         char[504] message;
     };

:/
Jun 30 2020