My view is that a C implementation cannot satisfy the specification of certain stdio functions (particularly fputc/fgetc) if sizeof(int)==1, since the int needs to be able to hold any possible value of unsigned char or EOF (-1). Is this reasoning correct?
(Obviously sizeof(int) cannot be 1 if CHAR_BIT is 8, due to the minimum required range for int, so we're implicitly only talking about implementations with CHAR_BIT>=16, for instance DSPs, where typical implementations would be a freestanding implementation rather than a hosted implementation, and thus not required to provide stdio.)
Edit: After reading the answers and some links references, some thoughts on ways it might be valid for a hosted implementation to have sizeof(int)==1:
First, some citations:
7.19.7.1(2-3):
If the end-of-file indicator for the input stream pointed to by stream is not set and a next character is present, the fgetc function obtains that character as an unsigned char converted to an int and advances the associated file position indicator for the stream (if defined).
If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the endof-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the fgetc function returns the next character from the input stream pointed to by stream. If a read error occurs, the error indicator for the stream is set and the fgetc function returns EOF.
7.19.8.1(2):
The fread function reads, into the array pointed to by ptr, up to nmemb elements whose size is specified by size, from the stream pointed to by stream. For each object, size calls are made to the fgetc function and the results stored, in th