Null pointer warning in adler.c (static analysis)

[irwir]

zlib/adler32.c

Lines 69 to 71 in 2896db6

	/* in case user likes doing a byte at a time, keep it fast */
	if (len == 1) {
	adler += buf[0];

Suspicious to code analyzer is dereferencing buf while the pointer is checked for null later.

The function declared as ZEXPORT presumably could be called by user with these arguments: adler32_z(0, NULL, 1).
Code could be made safe by moving the NULL check up, before the quoted code.
The point of keeping it fast is a small excuse, because making a call for every single byte is certainly not about speed, while the additional check needs only two instructions (at least, for x86/x64).

The warning could be suppressed by replacing buf == Z_NULL with len == 0, but the code would be less safe.

[madler]

Not an issue. The code is written as intended, and a NULL pointer with a non-zero length is an error on the part of the application.