[xml] [PATCH] Signed vs. unsigned comparison warnings in dict.c

[Peter Kasting <pkasting google com>]

When compiled in MSVC, dict.c triggers warning C4018 for comparing signed and unsigned values in two places.

In both cases, the code basically does:

if (pool->end - pool->free > unsigned int) ...

The type of the LHS here is ptrdiff_t, which is signed.  When comparing signed to unsigned values, the compiler will convert the signed value to an unsigned value.  So if pool->end < pool->free, the comparison will almost always succeed, which was probably not the intent.

The attached patch is one conservative way to fix this, which should be correct in all cases on all platforms.  Another route, if you know that pool->end >= pool->free in all cases, would be to simply cast to size_t without additional checks.  Yet another route, if you knew the above AND that the difference would fit in an unsigned int, would be to unconditionally cast to unsigned int.

This seems to be the only place preventing Chromium from compiling libxml with this warning enabled (which is the default state for this warning), so it would be nice to fix.  The attached patch was generated from an older copy of the libxml sources, but I think should still apply (possibly with a slight offset) to the current tree.

PK

Attachment: xml_signedness.patch
Description: Binary data