On 5/3/20 6:32 AM, Philippe Mathieu-Daudé wrote:
When building with Clang 10 on Fedora 32, we get:
CC linux-user/mmap.o
linux-user/mmap.c:720:49: error: result of comparison 'unsigned long' >
18446744073709551615 is always false [-Werror,-Wtautological-type-limit-compare]
if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~
Fix by restricting the check for when target sizeof(abi_ulong) is
smaller than target sizeof(unsigned long).
Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org>
---
linux-user/mmap.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index e378033797..b14652d894 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -714,6 +714,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong
old_size,
errno = ENOMEM;
host_addr = MAP_FAILED;
}
+#if TARGET_ABI_BITS < TARGET_LONG_BITS
/* Check if address fits target address space */
if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
Instead of using #if, the following suffices to shut up clang:
diff --git c/linux-user/mmap.c w/linux-user/mmap.c
index e37803379747..8d9ba201625d 100644
--- c/linux-user/mmap.c
+++ w/linux-user/mmap.c
@@ -715,7 +715,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong
old_size,
host_addr = MAP_FAILED;
}
/* Check if address fits target address space */
- if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
+ if ((unsigned long)host_addr > (abi_ulong)-1 - new_size) {
/* Revert mremap() changes */
host_addr = mremap(g2h(old_addr), new_size, old_size, flags);
errno = ENOMEM;
That is, it is no longer a tautological type compare if you commute the
operations so that neither side is a compile-time constant.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
