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Make memcpy volatile to make sure bytes are copied and not optimized out by the compiler.

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This commit is contained in:
Ion Gaztañaga
2015-12-24 10:39:24 +01:00
parent 827f6de30e
commit c4faf26527
1 changed files with 57 additions and 10 deletions
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67
test/unique_ptr_functions.cpp
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@@ -47,33 +47,79 @@ static const unsigned char ee_patternbuf[PatternSize] = { 0xEE, 0xEE, 0xEE, 0xEE
static const unsigned char dd_patternbuf[PatternSize] = { 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD };
static const unsigned char cc_patternbuf[PatternSize] = { 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC };
void volatile_memset(volatile void *p, int ch, std::size_t len)
{
volatile unsigned char *puch = static_cast<volatile unsigned char *>(p);
for(std::size_t i = 0; i != len; ++i){
*puch = (unsigned char)ch;
++puch;
}
}
int volatile_memcmp(const volatile void *p1, const volatile void *p2, std::size_t len)
{
const volatile unsigned char *s1 = static_cast<const volatile unsigned char *>(p1);
const volatile unsigned char *s2 = static_cast<const volatile unsigned char *>(p2);
unsigned char u1, u2;
for ( ; len-- ; s1++, s2++) {
u1 = *s1;
u2 = *s2;
if (u1 != u2) {
return (u1-u2);
}
}
return 0;
}
void volatile_memcmp(volatile void *p, int ch, std::size_t len)
{
volatile unsigned char *puch = static_cast<volatile unsigned char *>(p);
for(std::size_t i = 0; i != len; ++i){
*puch = (unsigned char)ch;
++puch;
}
}
#include <iostream>
struct default_init
{
static void* operator new(std::size_t sz)
{
void *const p = ::operator new(sz);
return std::memset(p, 0xFF, sz);
//Make sure they are not optimized out
volatile_memset(p, 0xFF, sz);
std::cout << "0xFF" << '\n';
return p;
}
static void* operator new[](std::size_t sz)
{
void *const p = ::operator new[](sz);
return std::memset(p, 0xEE, sz);
//Make sure they are not optimized out
volatile_memset(p, 0xEE, sz);
std::cout << "0xEE" << '\n';
return p;
}
static void* operator new(std::size_t sz, const std::nothrow_t &)
{
void *const p = ::operator new(sz);
return std::memset(p, 0xDD, sz);
//Make sure they are not optimized out
volatile_memset(p, 0xDD, sz);
std::cout << "0xDD" << '\n';
return p;
}
static void* operator new[](std::size_t sz, const std::nothrow_t &)
{
void *const p = ::operator new[](sz);
return std::memset(p, 0xCC, sz);
//Make sure they are not optimized out
volatile_memset(p, 0xCC, sz);
std::cout << "0xCC" << '\n';
return p;
}
unsigned char buf[PatternSize];
};
namespace bml = ::boost::movelib;
////////////////////////////////
@@ -88,11 +134,12 @@ void test()
reset_counters();
{
bml::unique_ptr<default_init> p(bml::make_unique_definit<default_init>());
BOOST_TEST(0 == std::memcmp(p.get(), ff_patternbuf, sizeof(ff_patternbuf)));
BOOST_TEST(0 == volatile_memcmp(p.get(), ff_patternbuf, sizeof(ff_patternbuf)));
}
{
bml::unique_ptr<default_init> p(bml::make_unique_nothrow_definit<default_init>());
BOOST_TEST(0 == std::memcmp(p.get(), dd_patternbuf, sizeof(dd_patternbuf)));
BOOST_TEST(0 == volatile_memcmp(p.get(), dd_patternbuf, sizeof(dd_patternbuf)));
}
BOOST_TEST(A::count == 0);
@@ -167,14 +214,14 @@ void test()
{
bml::unique_ptr<default_init[]> p(bml::make_unique_definit<default_init[]>(10));
for(unsigned i = 0; i != 10; ++i){
BOOST_TEST(0 == std::memcmp(&p[i], ee_patternbuf, sizeof(ee_patternbuf)));
BOOST_TEST(0 == volatile_memcmp(&p[i], ee_patternbuf, sizeof(ee_patternbuf)));
}
}
reset_counters();
{
bml::unique_ptr<default_init[]> p(bml::make_unique_nothrow_definit<default_init[]>(10));
for(unsigned i = 0; i != 10; ++i){
BOOST_TEST(0 == std::memcmp(&p[i], cc_patternbuf, sizeof(cc_patternbuf)));
BOOST_TEST(0 == volatile_memcmp(&p[i], cc_patternbuf, sizeof(cc_patternbuf)));
}
}
}