conflicting types for '_putchar'

Question

Hello, 
 There's a problem compiling the standard ble_app_uart_pca10040_s132 in Segger Embedded Studio for ARM V3.40. The UART example is straight out of nRF5_SDK_14.2.0_17b948a. 
 The exact same example can be compiled OK in SES V3.34. 
 The error message in V3.40 is 
 
 conflicting types for '__putchar' 
 retarget.c 
 previous declaration of '__putchar' was here 
 
 That line points to stdio.h declaration of __puchar

Martin Lesund · Accepted Answer

Hi Winston, 
 SEGGER has added the prototype for _putchar() in stdio.h, but the declaration of this prototype has a different type of variable. 
 See below: 
 stdio.h (line 773) 
 // Macro version of putchar.
#ifndef __PRINTF_TAG_PTR_DEFINED
#define __PRINTF_TAG_PTR_DEFINED
typedef struct __printf_tag *__printf_tag_ptr;
#endif
int __putchar(int, __printf_tag_ptr);
#define putchar(x) __putchar(x, 0)

Solution: 
 To solve this issue, we need to change the type of value in __putchar to __printf_tag_ptr instead of FILE *. 
 before: (retarget.c, line100) 
 int __putchar(int ch, FILE * p_file)
{
 UNUSED_PARAMETER(p_file);

 UNUSED_VARIABLE(app_uart_put((uint8_t)ch));
 return ch;
}
 
 after: 
 int __putchar(int ch, __printf_tag_ptr p_file)
{
 UNUSED_PARAMETER(p_file);

 UNUSED_VARIABLE(app_uart_put((uint8_t)ch));
 return ch;
}

conflicting types for '_putchar'

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Solution: