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// Author: Michael Chastain
//
// This is a unit test for large allocations in malloc and friends.
// "Large" means "so large that they overflow the address space".
// For 32 bits, this means allocations near 2^32 bytes and 2^31 bytes.
// For 64 bits, this means allocations near 2^64 bytes and 2^63 bytes.
#include <stddef.h> // for size_t, NULL
#include <stdlib.h> // for malloc, free, realloc
#include <stdio.h>
#include <set> // for set, etc
#include "base/logging.h" // for operator<<, CHECK, etc
using std::set;
// Alloc a size that should always fail.
void TryAllocExpectFail(size_t size) {
void* p1 = malloc(size);
CHECK(p1 == NULL);
void* p2 = malloc(1);
CHECK(p2 != NULL);
void* p3 = realloc(p2, size);
CHECK(p3 == NULL);
free(p2);
}
// Alloc a size that might work and might fail.
// If it does work, touch some pages.
void TryAllocMightFail(size_t size) {
unsigned char* p = static_cast<unsigned char*>(malloc(size));
if ( p != NULL ) {
unsigned char volatile* vp = p; // prevent optimizations
static const size_t kPoints = 1024;
for ( size_t i = 0; i < kPoints; ++i ) {
vp[i * (size / kPoints)] = static_cast<unsigned char>(i);
}
for ( size_t i = 0; i < kPoints; ++i ) {
CHECK(vp[i * (size / kPoints)] == static_cast<unsigned char>(i));
}
vp[size-1] = 'M';
CHECK(vp[size-1] == 'M');
}
free(p);
}
int main (int argc, char** argv) {
// Allocate some 0-byte objects. They better be unique.
// 0 bytes is not large but it exercises some paths related to
// large-allocation code.
{
static const int kZeroTimes = 1024;
printf("Test malloc(0) x %d\n", kZeroTimes);
set<char*> p_set;
for ( int i = 0; i < kZeroTimes; ++i ) {
char* p = new char;
CHECK(p != NULL);
CHECK(p_set.find(p) == p_set.end());
p_set.insert(p_set.end(), p);
}
// Just leak the memory.
}
// Grab some memory so that some later allocations are guaranteed to fail.
printf("Test small malloc\n");
void* p_small = malloc(4*1048576);
CHECK(p_small != NULL);
// Test sizes up near the maximum size_t.
// These allocations test the wrap-around code.
printf("Test malloc(0 - N)\n");
const size_t zero = 0;
static const size_t kMinusNTimes = 16384;
for ( size_t i = 1; i < kMinusNTimes; ++i ) {
TryAllocExpectFail(zero - i);
}
// Test sizes a bit smaller.
// The small malloc above guarantees that all these return NULL.
printf("Test malloc(0 - 1048576 - N)\n");
static const size_t kMinusMBMinusNTimes = 16384;
for ( size_t i = 0; i < kMinusMBMinusNTimes; ++i) {
TryAllocExpectFail(zero - 1048576 - i);
}
// Test sizes at half of size_t.
// These might or might not fail to allocate.
printf("Test malloc(max/2 +- N)\n");
static const size_t kHalfPlusMinusTimes = 64;
const size_t half = (zero - 2) / 2 + 1;
for ( size_t i = 0; i < kHalfPlusMinusTimes; ++i) {
TryAllocMightFail(half - i);
TryAllocMightFail(half + i);
}
printf("PASS\n");
return 0;
}