i want to see output of Preprocessor calculating. Only with strings it works so:
#define XSTR(x) STR(x)
#define STR(x) #x
#define BEGIN "test"
#pragma message ".text= " XSTR(BEGIN)
when i set BEGIN to 32/2 the output is: #pragma message: .text= 32/2.
What can i make to solve this? I don´t won´t solutions like this to search in the .lss file:
uint16_t x = BEGIN;
PORTB = x>>8;
PORTA = x;
Thank you.
What can i make to solve this?
You have to implement math operations in the preprocessor. For example:
#define _div_1_over_1 1
#define _div_2_over_1 2
#define _div_3_over_1 3
// etc...
#define _div_30_over_2 15
#define _div_31_over_2 15
#define _div_32_over_2 16
// etc...
// etc. for every possible a_over_b combinations, many many 1000 lines
#define DIV(a, b) _div_##a##_over_##b
After that, you finally can:
#define XSTR(x) STR(x)
#define STR(x) #x
#define BEGIN DIV(32, 2)
#pragma message ".text= " XSTR(BEGIN)
Let's say this is one way of implementing division in preprocessor. For other solutions, see BOOST_PP_DIV and P99_DIV from p99 library.
The C preprocessor just performs text replacement(s).
The first opportunity to see folded constants is in the tree dumps with -fdump-tree-all and then inspect the *.t<nnn> dumps.
To get the asm output from the compiler proper, try -safe-temps -fverbose-asm which inserts C source intermingled as asm comments in the *.s file.
BEGINto32/2?#ifconditions. You won't get it to calculate and print something (let's ignore abominations like BOOST_PP). See also: stackoverflow.com/questions/1560357/…