%zu not supported by newlib's printf in Arduino_STM32 toolchain

[fronders]

People have been reporting same problem when using newlib printf. This is what's included into Arduino STM32 toolchain and so the %zu format specifier doesn't work, and instead of putting the number it puts "zu" into the resulting string.

As a consequence the getFileBlock() just freezes and never returns

SparkFun_u-blox_SARA-R5_Arduino_Library/src/SparkFun_u-blox_SARA-R5_Arduino_Library.cpp

Lines 5602 to 5605 in d35bce3

	size_t cmd_len = filename.length() + 32;
	char* cmd = sara_r5_calloc_char(cmd_len);
	sprintf(cmd, "at+urdblock=\"%s\",%zu,%zu\r\n", filename.c_str(), offset, requested_length);
	sendCommand(cmd, false);

Here's the debugger screenshot:

Changing those to %lu fixes the issue.

UPD:
By default, the sketches use newlib nano option which passes linker flags --specs=nano.specs
I'm usually compiling using the "newlib nano + float printf" which is --specs=nano.specs -u _printf_float cause I need floats support in printfs. After switching to the full-featured "newlib standard" (which doesn't pass any additional flags) the %zu specifier worked! I assume the nano option supplied with ARM toolchain newlib is built without C99 formatting support. But I don't use it because it makes the flash size (program storage space) explode - the same sketch went from 82376 to 188208 bytes, as well as RAM went +1kB!

[PaulZC]

Hi @fronders ,

Glad you got it working. How would you like to resolve this? I am happy to pin it, to make it easier for others to find and re-use your solution.

Best wishes,
Paul

[fronders]

Hi @PaulZC,

I think the best would be to update the code to make it usable for everyone, even ARM toolchain with nano version of newlib.
See the PR with some more fixes :)