C中stm32l中的数据损坏

Question

I am finding some data corruption in the variable u32baudrate, when passed from main to httpinit(). But other variables txsize and flowcontrol are coming out right.

typedef struct _test
{
  ...
  uint8_t txsize[5];
  uint32_t u32baudrate;
  uint8_t flowcontrol;
  ...
}test;

from main.c

test gtest;
gtest.u32baudrate=921600;
printf("baud: %d",gtest.u32baudrate);        //921600: this is coming out right

httpinit(&gtest);

in http.c

httpinit(test * gtest)
{
  printf("baud: %d",gtest->u32baudrate);     //268435456: this is coming out wrong
}

Answer 1

Found the problem, it was packing, fixed it by doing this-->

typedef PACKED struct _test
{
  ...
  uint8_t txsize[5];
  uint32_t u32baudrate;
  uint8_t flowcontrol;
  ...
}test;

Answer 2

I think this may help, well not sure :)

typedef struct    //delete this so test is the struct type name// _test
{
  ...
  uint8_t txsize[5];
  uint32_t u32baudrate;
  uint8_t flowcontrol;
  ...
}test;

Answer 3

The problem is quite possibly in code you have not posted.

Some printf() implementations use a relatively large amount of stack; you may have a stack-overflow caused by your debug method. Try removing the first printf call so that there is nothing between the assignment and the httptest() call. If it is then not corrupted, the printf() itself caused the problem, and you probably need to assign a larger stack.

Otherwise an out-of-bounds access to txsize[] is a possibility. Is this truly the code you are testing - with httptest() called directly after assignment - or have you elided the code presented?

Answer 4

The printf() format specifier %d is used to print signed integers. However, uint32_t is an unsigned integer type. The usual format specifier for unsigned ints is %u .

Answer 5

Packed has nothing to do with this error. Usually, an error on a printf results form stack corruption. Consider this:

struct wp_char{
      char wp_cval;
      short wp_font;
      short wp_psize;
}v1;

struct wp_char v2;

What is the difference between v1 and v2? Are they different or same? Oops....pressed the enter key by mistake.

BTW the following code works for me perfectly.

#include <stdio.h>
#include <limits.h>

typedef unsigned char uint8_t;
typedef unsigned int uint32_t;

typedef struct _test
{
    uint8_t txsize[5];
    uint32_t u32baudrate;
    uint8_t flowcontrol;
}test;

print_value(test *gtest)
{
        printf("%u\n", gtest->u32baudrate);
}

main()
{
        test gtest;

        gtest.u32baudrate = 921600;
        printf("%u\n", gtest.u32baudrate);

        print_value(&gtest);
}