devkitarm: file read data corruption

[bgK]

While investigating this downstream bug, I've noticed an issue with a patch devkitPro does to newlib's fread function: https://bugs.scummvm.org/ticket/11342

The program does the following calls to trigger data corruption:

	char *buffer = (char *)malloc(20*1024);

	// Open a file for reading with buffered IO
	FILE *f = fopen("sdmc:/ScummVM/The Dig/DIG.LA1", "r");

	// Go somewhere in the file, unimportant
	fseek(f, 23800663, SEEK_SET);
	// Initialize the stdio read buffer
	fread(buffer, 1, 1, f);
	// Make a large read that enters devkitPro's fread patched code path.
	// After this, the stdio read buffer is out of sync with the stream position.
	fread(buffer, 1, 10096, f);
	// Seek back a bit in the file. The target seek position is inside the buffer from
	// stdio's perspective (but actually is not as the buffer is out of sync with the actual
	// stream position).
	fseek(f, 23810752, SEEK_SET);
	// Make a small read. The data is fetched from the stdio buffer. It is inconsistent with what is actually in the file.
	fread(buffer, 1, 4, f);

	fclose(f);

I suggest reverting this patch:

newlib/newlib/libc/stdio/fread.c

Line 231 in a7caafc

if (resid>BUFSIZ)

[fgsfdsfgs]

Can confirm I've encountered this bug on Switch, especially when reading large files like PK3 archives in Quake 3.

[mtheall]

I have tested with the fread.c file reverted to original newlib code and this sequence of events still reads the wrong data.

False alarm

[WinterMute]

this is fixed with devkitARM r54 and devkitA64 r15