C + + inverse vector

Recently, the reverse of the Android/C + +, found that C + + classes, STL templates, in reverse when compared to the C language has brought no small difficulties.

Today I wrote a small program, and then reversed the analysis

Vector<int> Array_int;array_int.push_back (1); Array_int.push_back (2); Array_int.push_back (5);

Define a vector, and then add the data.

Ida disassembly is as follows: (comments added)

.Text:00001164int_tmp = -0x18.Text:00001164vector_ptr = -0x14.Text:00001164Var_8 =-8.Text:00001164.Text:00001164                 PUSH{R4-R7,LR}.Text:00001166LDR R5, = (__stack_chk_guard_ptr-0x1170).Text:00001168                 SUBsp, SP, #0x1C.Text:0000116AMOVS R4, #0.Text:0000116C                 ADDR5, PC;__stack_chk_guard_ptr.Text:0000116ELDR R5, [R5];__stack_chk_guard.Text:00001170                 ADDR6, SP, #0x1C +vector_ptr.Text:00001172                 ADDR7, SP, #4      ;[SP, #0x1C +int_tmp].Text:00001174LDR R3, [R5].Text:00001176MOVS R0, R6.Text:00001178                 STRR3, [SP, #0x1C +var_8].Text:0000117AMOVS R3, #1.Text:0000117CMOVS R1, R7.Text:0000117E                 STRR3, [SP, #0x1C +int_tmp].Text:00001180                 STRR4, [SP, #0x1C +vector_ptr].Text:00001182                 STRR4, [r6,#4].Text:00001184                 STRR4, [r6,#8].Text:00001186BL _znst6vectoriisaiiee9push_backerki;std::vector<int,std::allocator<int>>::p ush_back (int const&).Text:0000118AMOVS R3, #2.Text:0000118CMOVS R0, R6.Text:0000118EMOVS R1, R7.Text:00001190                 STRR3, [SP, #0x1C +int_tmp].Text:00001192BL _znst6vectoriisaiiee9push_backerki;std::vector<int,std::allocator<int>>::p ush_back (int const&).Text:00001196MOVS R3, #5.Text:00001198MOVS R0, R6.Text:0000119AMOVS R1, R7.Text:0000119C                 STRR3, [SP, #0x1C +int_tmp].Text:0000119EBL _znst6vectoriisaiiee9push_backerki;std::vector<int,std::allocator<int>>::p ush_back (int const&)

The analysis is as follows:

. Text: 00001170                 ADD     R6, SP, #0x1C +vector_ptr

Copy the address at the vector_ptr of the stack to R6

. Text: 00001172                 ADD     R7, SP, #4      ; [SP, #0x1C +int_tmp]

Assign the address of the sp+4 to R7, which is equivalent to the int_tmp at the stack

. Text: 00001176                 MOVS    R0, R6

Assigns the address of the vector_ptr to R0 as the first parameter of the Push_back

. text:  0000116a  MOVS R4, #0   (the order has been adjusted to see the address number).  text:  0000117a  MOVS R3, #1  . text:  0000117c   MOVS R1, R7.  text:  0000117e   R3, [SP, #0x1C +int_tmp].  text:  00001180   R4, [SP, #0x1C +vector_ptr]  

The int value 1 that will be push_back is stored at the int_tmp of the stack. Assign R7 to R1 as the second parameter of Push_back, the first parameter is a vector object pointer, which is the this pointer.

Assigns a value of 0 to the vector_ptr.

. Text: 00001182                 STR     R4, [r6,#4]. Text: 00001184                 STR     R4, [r6,#8]

Assigns a value of 0 to the last two stacks in the vector_ptr, where [R6, #4] holds a pointer to the next item in the vector, equivalent to end ().

The value of [R6, #8] will change with the push_back, but it's not found yet.

. Text: 00001186                 BL      ; std::vector<int,std::allocator<int>>::p ush_back (int const&)

Executive Push_back (R0,R1)

This is the address of the vector_ptr in R0 (the value at address is 0), the address of R1 is int_tmp (the value at address is the data to be added 1)

When you finish executing this sentence, the value at the VECTOR_PTR address is modified to the address of the object array_int.

At each subsequent push_back () operation, Vector_ptr, Vector_ptr+4, the value at Vector_ptr+8 will change.

The corresponding function prototype is push_back (vector<int>*,int*)

Debug results:

First time Push_back

Second time Push_back

Third time Push_back

C + + inverse vector