Scanf scientific notation floats problem

[maska989]

During scanf tests there was a problem reading floats in scientific notation

The problem occurs in an all-conversion specifier wich can handle that (%aAeEgGfF).

• On reproducing this issue was used commit with sha number "bd57fdd3746e40dd60989277002ff949fcf0a348"
• To reproduce issue copy following code:

  
  #include <stdio.h>

int main(void) { float test;

printf("\n%f\n", 3.40282347e+38F);
printf("\n%F\n", 3.40282347e+38F);
printf("\n%a\n", 3.40282347e+38F);
printf("\n%A\n", 3.40282347e+38F);
printf("\n%e\n", 3.40282347e+38F);
printf("\n%E\n", 3.40282347e+38F);
printf("\n%g\n", 3.40282347e+38F);
printf("\n%G\n", 3.40282347e+38F);

sscanf("3.40282347e+38F", "%f", &test);
printf("\n%f\n", test);
sscanf("3.40282347e+38F", "%F", &test);
printf("\n%F\n", test);
sscanf("3.40282347e+38F", "%a", &test);
printf("\n%a\n", test);
sscanf("3.40282347e+38F", "%A", &test);
printf("\n%A\n", test);
sscanf("3.40282347e+38F", "%e", &test);
printf("\n%e\n", test);
sscanf("3.40282347e+38F", "%E", &test);
printf("\n%E\n", test);
sscanf("3.40282347e+38F", "%g", &test);
printf("\n%g\n", test);
sscanf("3.40282347e+38F", "%G", &test);
printf("\n%G\n", test);

}

 - Outcome on Host-generic-pc and ia32-generic-qemu:
![Screenshot from 2023-03-08 14-40-14](https://user-images.githubusercontent.com/49757239/223732167-0f61af6d-d173-470b-9bc5-61f561a80b5f.png)

[gerard5]

The scanf() implementation uses three functions strtof(), strtod(), strtold() to read and convert float/double/long double values. So the root problem is not in scanf() itself, but in the limited implementation of strtold() which is common base to the other two functions.

strtoll(), strtoul(), .. strtold(), strtod(), strtof() should be tested first as other functions like e.g. scanf(), atoi(), etc.. benefit from the implementation of the above-mentioned base functions so as not to "reinvent the wheel".

https://github.com/phoenix-rtos/libphoenix/blob/e913aa45b783bbc630dafac0ee36871a6a2324d9/stdio/scanf.c#L548 https://github.com/phoenix-rtos/libphoenix/blob/e913aa45b783bbc630dafac0ee36871a6a2324d9/stdio/scanf.c#L568-L580

So this also applies for issue https://github.com/phoenix-rtos/phoenix-rtos-project/issues/634 about: NaN and INFinity as strtold() needs to support and for which strtold() support should be tested first.

[damianloew]

Yeah thanks for noticing that, there already is such test (https://github.com/phoenix-rtos/phoenix-rtos-tests/pull/135). We will add similar cases to it and update issue with the code to reproduce using strto* functions. Applies also for https://github.com/phoenix-rtos/phoenix-rtos-project/issues/634

[maska989]

@gerard5 I'm sorry for the lousy issue caused by a poorly selected available branch on libphoenix. Once again sorry for wasting time.