32 位模式下 C/C++ 程序到底可以用多少内存

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32位的程序寻址空间是 4G，因此能用的内存应该有 4G，除掉一些系统等使用的乱七八糟的东西，3G内存应该没有问题吧，这些只是猜测，写个程序测一下，结果如下：测试结论：1. 栈内存最大可用 768k左右；2. 堆内存最大可用 1.586G左右。结果令人沮丧，才 1.6 G!!! 测试环境：Windows7 2G、IBMSL300、VC9附录测试程序等测试程序只考虑 windows，首先，说明一下相关知识：内存可以来自两个地方，在栈空间上分配的内存（栈内存）和在堆空间分配的内存（堆内存）。栈内存，通过 alloca来申请。堆内存，通过 malloc、new、VirtualAlloc来申请。测试程序如下：/* $Id$ *//*** \file memory_test.cpp** \brief大内存申请测试** \version $Rev$* \author * \date 2010年04月06日:09:24** \note修改历史：<br>* <table>* <tr><th>日期</th><th>修改人</th><th>内容</th></tr>* <tr><td>2010-4-6</td><td></td><td>创建初稿</td>* </tr>* </table>*/#include<stdio.h>#include<malloc.h>#include<windows.h>#include<excpt.h> // alloca: Allocates memory on the stackstaticbool alloca_test(size_ts){ __try{ alloca(s); printf(" √1 alloca(%u)通过\n",s); }__except(GetExceptionCode() == STATUS_STACK_OVERFLOW ){ printf(" ×1 alloca(%u)失败，内存溢出\n",s); _resetstkoflw(); return false; } __try{ alloca(s); printf(" √2 alloca(%u)通过\n",s); }__except(GetExceptionCode() == STATUS_STACK_OVERFLOW ){ printf(" ×2 alloca(%u)失败，内存溢出\n",s); _resetstkoflw(); return false; } return true;}// malloc: Allocates memory blocks.staticbool malloc_test(size_ts){ void* buf = malloc(s); if (buf) printf(" √malloc(%u)通过\n",s); else printf(" ×malloc(%u)失败\n",s); free(buf); return buf != 0;}// malloc: Allocates memory blocks.staticbool malloc_test2(size_ts){ void* buf1 = malloc(s); void* buf2 = malloc(s); if (buf1) printf(" √buf1 malloc(%u)通过\n",s); else printf(" ×buf1 malloc(%u)失败\n",s); if (buf2) printf(" √buf2 malloc(%u)通过\n",s); else printf(" ×buf2 malloc(%u)失败\n",s); free(buf1); free(buf2); return buf1 != 0 &&buf2 != 0;}staticbool new_test(size_ts){ try { char* buf = new char[s]; delete[] buf; printf(" √new char[%u]成功\n",s); return true; }catch(...){ printf(" ×new char[%u]失败\n",s); return false; }}boolVirtualAlloc_test(size_ts){ LPVOID buf =VirtualAlloc(NULL,s, MEM_COMMIT,PAGE_READWRITE); VirtualFree(buf, 0,MEM_RELEASE); if (buf) printf(" √VirtualAlloc(NULL, %u, ..)成功\n",s); else printf(" ×VirtualAlloc(NULL, %u, ..)失败\n",s); return buf != 0;}boolVirtualAlloc_test2(size_ts){ LPVOID buf1 =VirtualAlloc(NULL,s, MEM_COMMIT,PAGE_READWRITE); LPVOID buf2 =VirtualAlloc(NULL,s, MEM_COMMIT,PAGE_READWRITE); VirtualFree(buf1, 0,MEM_RELEASE); VirtualFree(buf2, 0,MEM_RELEASE); if (buf1) printf(" √1 VirtualAlloc(NULL, %u, ..)成功\n",s); else printf(" ×1 VirtualAlloc(NULL, %u, ..)失败\n",s); if (buf2) printf(" √2 VirtualAlloc(NULL, %u, ..)成功\n",s); else printf(" ×2 VirtualAlloc(NULL, %u, ..)失败\n",s); return buf1 != 0 &&buf2 != 0;}constsize_t SIZE_K = (((size_t)1) << 10);constsize_t SIZE_M = (SIZE_K << 10);constsize_t SIZE_G = (SIZE_M << 10);//把大小转换为xxxK、xxxM、xxxG 之类的描述，非线程安全！staticchar const*consti2a(size_t s){ static char buf[24]; if (s < SIZE_M) { sprintf(buf,"%uK", s/SIZE_K); }else if (s <SIZE_G) { sprintf(buf,"%.3fM", (double)s/SIZE_M); }else { sprintf(buf,"%.3fG", (double)s/SIZE_G); } return buf;}intmain(int, char**){ size_t sizes[] = { SIZE_K // 1K , 128*SIZE_K // 128K , 256*SIZE_K // 256K , 512*SIZE_K // 512K , 768*SIZE_K // 768K ,SIZE_M // 1M , 512*SIZE_M // 512M , 640*SIZE_M // 640M , 768*SIZE_M // 768M ,SIZE_G // 1G ,SIZE_G + 100*SIZE_M// 1.1G ,SIZE_G + 200*SIZE_M// 1.2G ,SIZE_G + 300*SIZE_M// 1.3G ,SIZE_G + 400*SIZE_M// 1.4G ,SIZE_G + 500*SIZE_M// 1.5G ,SIZE_G + 600*SIZE_M// 1.6G ,SIZE_G + 700*SIZE_M// 1.7G ,SIZE_G + 800*SIZE_M// 1.8G ,SIZE_G + 900*SIZE_M// 1.9G }; printf("大内存申请测试\n"); bool res = true; for (size_t i = 0, c = sizeof(sizes)/sizeof(sizes[0]);i != c && res; ++i) { size_t s = sizes[i]; printf(" 测试申请%s 内存\n",i2a(s)); res = false; res = alloca_test(s) ||res; res = malloc_test(s) ||res; res = new_test(s) ||res; res = VirtualAlloc_test(s) ||res; if (s >= 1024*1024*512) { res = malloc_test2(s) ||res; res = VirtualAlloc_test2(s) ||res; } } return 0;}运行结果如下：大内存申请测试 测试申请 1K内存 √ 1 alloca(1024)通过 √ 2 alloca(1024)通过 √ malloc(1024)通过 √ new char[1024]成功 √ VirtualAlloc(NULL, 1024, ..)成功 测试申请 128K内存 √ 1 alloca(131072)通过 √ 2 alloca(131072)通过 √ malloc(131072)通过 √ new char[131072]成功 √ VirtualAlloc(NULL, 131072, ..)成功 测试申请 256K内存 √ 1 alloca(262144)通过 √ 2 alloca(262144)通过 √ malloc(262144)通过 √ new char[262144]成功 √ VirtualAlloc(NULL, 262144, ..)成功 测试申请 512K内存 √ 1 alloca(524288)通过 × 2 alloca(524288)失败，内存溢出 √ malloc(524288)通过 √ new char[524288]成功 √ VirtualAlloc(NULL, 524288, ..)成功 测试申请 768K内存 √ 1 alloca(786432)通过 × 2 alloca(786432)失败，内存溢出 √ malloc(786432)通过 √ new char[786432]成功 √ VirtualAlloc(NULL, 786432, ..)成功 测试申请 1.000M内存 × 1 alloca(1048576)失败，内存溢出 √ malloc(1048576)通过 √ new char[1048576]成功 √ VirtualAlloc(NULL, 1048576, ..)成功 测试申请 512.000M内存 × 1 alloca(536870912)失败，内存溢出 √ malloc(536870912)通过 √ new char[536870912]成功 √ VirtualAlloc(NULL, 536870912, ..)成功 √ buf1 malloc(536870912)通过 √ buf2 malloc(536870912)通过 √ 1 VirtualAlloc(NULL, 536870912, ..)成功 √ 2 VirtualAlloc(NULL, 536870912, ..)成功 测试申请 640.000M内存 × 1 alloca(671088640)失败，内存溢出 √ malloc(671088640)通过 √ new char[671088640]成功 √ VirtualAlloc(NULL, 671088640, ..)成功 √ buf1 malloc(671088640)通过 √ buf2 malloc(671088640)通过 √ 1 VirtualAlloc(NULL, 671088640, ..)成功 √ 2 VirtualAlloc(NULL, 671088640, ..)成功 测试申请 768.000M内存 × 1 alloca(805306368)失败，内存溢出 √ malloc(805306368)通过 √ new char[805306368]成功 √ VirtualAlloc(NULL, 805306368, ..)成功 √ buf1 malloc(805306368)通过 √ buf2 malloc(805306368)通过 √ 1 VirtualAlloc(NULL, 805306368, ..)成功 √ 2 VirtualAlloc(NULL, 805306368, ..)成功 测试申请 1.000G内存 × 1 alloca(1073741824)失败，内存溢出 √ malloc(1073741824)通过 √ new char[1073741824]成功 √ VirtualAlloc(NULL, 1073741824, ..)成功 √ buf1 malloc(1073741824)通过 × buf2 malloc(1073741824)失败 √ 1 VirtualAlloc(NULL, 1073741824, ..)成功 × 2 VirtualAlloc(NULL, 1073741824, ..)失败 测试申请 1.098G内存 × 1 alloca(1178599424)失败，内存溢出 √ malloc(1178599424)通过 √ new char[1178599424]成功 √ VirtualAlloc(NULL, 1178599424, ..)成功 √ buf1 malloc(1178599424)通过 × buf2 malloc(1178599424)失败 √ 1 VirtualAlloc(NULL, 1178599424, ..)成功 × 2 VirtualAlloc(NULL, 1178599424, ..)失败 测试申请 1.195G内存 × 1 alloca(1283457024)失败，内存溢出 √ malloc(1283457024)通过 √ new char[1283457024]成功 √ VirtualAlloc(NULL, 1283457024, ..)成功 √ buf1 malloc(1283457024)通过 × buf2 malloc(1283457024)失败 √ 1 VirtualAlloc(NULL, 1283457024, ..)成功 × 2 VirtualAlloc(NULL, 1283457024, ..)失败 测试申请 1.293G内存 × 1 alloca(1388314624)失败，内存溢出 √ malloc(1388314624)通过 √ new char[1388314624]成功 √ VirtualAlloc(NULL, 1388314624, ..)成功 √ buf1 malloc(1388314624)通过 × buf2 malloc(1388314624)失败 √ 1 VirtualAlloc(NULL, 1388314624, ..)成功 × 2 VirtualAlloc(NULL, 1388314624, ..)失败 测试申请 1.391G内存 × 1 alloca(1493172224)失败，内存溢出 √ malloc(1493172224)通过 √ new char[1493172224]成功 √ VirtualAlloc(NULL, 1493172224, ..)成功 √ buf1 malloc(1493172224)通过 × buf2 malloc(1493172224)失败 √ 1 VirtualAlloc(NULL, 1493172224, ..)成功 × 2 VirtualAlloc(NULL, 1493172224, ..)失败 测试申请 1.488G内存 × 1 alloca(1598029824)失败，内存溢出 √ malloc(1598029824)通过 √ new char[1598029824]成功 √ VirtualAlloc(NULL, 1598029824, ..)成功 √ buf1 malloc(1598029824)通过 × buf2 malloc(1598029824)失败 √ 1 VirtualAlloc(NULL, 1598029824, ..)成功 × 2 VirtualAlloc(NULL, 1598029824, ..)失败 测试申请 1.586G内存 × 1 alloca(1702887424)失败，内存溢出 √ malloc(1702887424)通过 √ new char[1702887424]成功 √ VirtualAlloc(NULL, 1702887424, ..)成功 √ buf1 malloc(1702887424)通过 × buf2 malloc(1702887424)失败 √ 1 VirtualAlloc(NULL, 1702887424, ..)成功 × 2 VirtualAlloc(NULL, 1702887424, ..)失败 测试申请 1.684G内存 × 1 alloca(1807745024)失败，内存溢出 × malloc(1807745024)失败 × new char[1807745024]失败 × VirtualAlloc(NULL, 1807745024, ..)失败 × buf1 malloc(1807745024)失败 × buf2 malloc(1807745024)失败 × 1 VirtualAlloc(NULL, 1807745024, ..)失败 × 2 VirtualAlloc(NULL, 1807745024, ..)失败