C ++ std :: vector insert segfault
I am writing a test program to understand better vector
. In one scenario I am trying insert
to assign a value to a vector at a specified position. The code compiles clean. However, when executed, it throws a segmentation fault from the string v8.insert(..)
(see code below). I'm confused. Can anyone point me to what is wrong in my code?
#define UNIT_TEST(x) assert(x)
#define ENSURE(x) assert(x)
#include <vector>
typedef std::vector< int > intVector;
typedef std::vector< int >::iterator intVectorIterator;
typedef std::vector< int >::const_iterator intVectorConstIterator;
intVectorIterator find( intVector v, int key );
void test_insert();
intVectorIterator
find( intVector v, int key )
{
for( intVectorIterator it = v.begin(); it != v.end(); ++it )
{
if( *it == key )
{
return it;
}
}
return v.end();
}
void
test_insert()
{
const int values[] = {10, 20, 30, 40, 50};
const size_t valuesLength = sizeof( values ) / sizeof( values[ 0 ] );
size_t index = 0;
const int insertValue = 5;
intVector v8;
for( index = 0; index < valuesLength; ++index )
{
v8.push_back( values[ index ] );
}
ENSURE( v8.size() == valuesLength );
for( index = 0; index < valuesLength; ++index )
{
printf( "index = %u\n", index );
intVectorIterator it = find( v8, values[ index ] );
ENSURE( it != v8.end() );
ENSURE( *it == values[ index ] );
// intVectorIterator itToInsertedItem =
v8.insert( it, insertValue ); // line 51
// UNIT_TEST( *itToInsertedItem == insertValue );
}
}
int main()
{
test_insert();
return 0;
}
$ ./a.out
index = 0
Segmentation Fault (core dumped)
(gdb) bt
#0 0xff3a03ec in memmove () from /platform/SUNW,T5140/lib/libc_psr.so.1
#1 0x00012064 in std::__copy_move_backward<false, true, std::random_access_iterator_tag>::__copy_move_b<int> (__first=0x23e48, __last=0x23450, __result=0x23454)
at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/stl_algobase.h:575
#2 0x00011f08 in std::__copy_move_backward_a<false, int*, int*> (__first=0x23e48, __last=0x23450, __result=0x23454)
at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/stl_algobase.h:595
#3 0x00011d00 in std::__copy_move_backward_a2<false, int*, int*> (__first=0x23e48, __last=0x23450, __result=0x23454)
at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/stl_algobase.h:605
#4 0x000119b8 in std::copy_backward<int*, int*> (__first=0x23e48, __last=0x23450, __result=0x23454) at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/stl_algobase.h:640
#5 0x000113ac in std::vector<int, std::allocator<int> >::_M_insert_aux (this=0xffbfeba0, __position=..., __x=@0xffbfebac)
at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/vector.tcc:308
#6 0x00011120 in std::vector<int, std::allocator<int> >::insert (this=0xffbfeba0, __position=..., __x=@0xffbfebac)
at /local/gcc/4.4.1/lib/gcc/sparc-sun-solaris2.10/4.4.1/../../../../include/c++/4.4.1/bits/vector.tcc:126
#7 0x00010bc0 in test_insert () at vector_insert_test.cpp:51
#8 0x00010c48 in main () at vector_insert_test.cpp:58
(gdb) q
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Your program is broken because it is missing two punctuation marks. :)
As written, when you call your own version of find (), a copy is made from your intVector and used by this function. When find () returns an iterator, it is a copy iterator, not v8. So when you call v8.insert () with another vector iterator, of course it will break.
The solution you are looking for is passing intVector by find () link. (ie add two "&" characters)
The best solution is to simply reuse std :: find ().
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