如何在C中打印出变量的内存内容？
假设我做了
double d = 234.5; 我想看看d [整个8字节]的内存内容
我怎么做？
double d = 234.5; /* 1. use a union */ union u { double d; unsigned char c[sizeof(double)]; }; union u tmp; size_t i; tmp.d = d; for (i=0; i < sizeof(double); ++i) printf("%02x\n", tmp.c[i]); /* 2. memcpy */ unsigned char data[sizeof d]; size_t i; memcpy(data, &d, sizeof d); for (i=0; i < sizeof d; ++i) printf("%02x\n", data[i]); /* 3. Use a pointer to an unsigned char to examine the bytes */ unsigned char *p = (unsigned char *)&d; size_t i; for (i=0; i < sizeof d; ++i) printf("%02x\n", p[i]);
所有方法都显示了字节 - 但是相同的double值可能会在不同系统上以不同方式打印字节，例如，由于编码不同（罕见）或不同的字节序。
unsigned char *p = (unsigned char *)&d; int i; for (i = 0; i < sizeof d; i++) printf("%02x ", p[i]);
由我的有用片段库提供，这是C语言的解决方案，包含测试工具，并提供hex和ASCII数据：
#include void hexDump (char *desc, void *addr, int len) { int i; unsigned char buff[17]; // stores the ASCII data unsigned char *pc = addr; // cast to make the code cleaner. // Output description if given. if (desc != NULL) printf ("%s:\n", desc); // Process every byte in the data. for (i = 0; i < len; i++) { // Multiple of 16 means new line (with line offset). if ((i % 16) == 0) { // Just don't print ASCII for the zeroth line. if (i != 0) printf (" %s\n", buff); // Output the offset. printf (" %04x ", i); } // Now the hex code for the specific character. printf (" %02x", pc[i]); // And store a printable ASCII character for later. if ((pc[i] < 0x20) || (pc[i] > 0x7e)) buff[i % 16] = '.'; else buff[i % 16] = pc[i]; buff[(i % 16) + 1] = '\0'; } // Pad out last line if not exactly 16 characters. while ((i % 16) != 0) { printf (" "); i++; } // And print the final ASCII bit. printf (" %s\n", buff); } int main (int argc, char *argv[]) { double d1 = 234.5; char s1[] = "a 15char string"; char s2[] = "This is a slightly longer string"; hexDump ("d1", &d1, sizeof d1); hexDump ("s1", &s1, sizeof s1); hexDump ("s2", &s2, sizeof s2); return 0; }
我系统的输出是：
d1: 0000 00 00 00 00 00 50 6d 40 .....Pm@ s1: 0000 61 20 31 35 63 68 61 72 20 73 74 72 69 6e 67 00 a 15char string. s2: 0000 54 68 69 73 20 69 73 20 61 20 73 6c 69 67 68 74 This is a slight 0010 6c 79 20 6c 6f 6e 67 65 72 20 73 74 72 69 6e 67 ly longer string 0020 00 .
由于这个问题也被标记为C ++，这里有一个比较的iostream版本。 即使你不是iostreams的特别粉丝，如果你已经在使用它们，它仍然适合。 能够使用hexdump(any_obj)也很不错，但当然可以使用类似于ctor的委托function模板来完成。
#include #include #include struct hexdump { void const* data; int len; hexdump(void const* data, int len) : data(data), len(len) {} template hexdump(T const& v) : data(&v), len(sizeof v) {} friend std::ostream& operator<<(std::ostream& s, hexdump const& v) { // don't change formatting for s std::ostream out (s.rdbuf()); out << std::hex << std::setfill('0'); unsigned char const* pc = reinterpret_cast(v.data); std::string buf; buf.reserve(17); // premature optimization int i; for (i = 0; i < v.len; ++i, ++pc) { if ((i % 16) == 0) { if (i) { out << " " << buf << '\n'; buf.clear(); } out << " " << std::setw(4) << i << ' '; } out << ' ' << std::setw(2) << unsigned(*pc); buf += (0x20 <= *pc && *pc <= 0x7e) ? *pc : '.'; } if (i % 16) { char const* spaces16x3 = " "; out << &spaces16x3[3 * (i % 16)]; } out << " " << buf << '\n'; return s; } }; int main() { std::cout << "double:\n" << hexdump(234.5); std::cout << "string 1:\n" << hexdump("a 15char string"); std::cout << "string 2:\n" << hexdump("This is a slightly longer string"); return 0; }
如果您想从gdb查看此内容，可以发出：
x /gx d
g会将值打印为巨型（8字节）
如果要以位为单位打印双值，请尝试此操作。 我试过浮动值。 如果更改了，则可以以64位查看double值。
#include int main (void) { float f = 10.0f; struct Float { unsigned char bit01:1; unsigned char bit02:1; unsigned char bit03:1; unsigned char bit04:1; unsigned char bit05:1; unsigned char bit06:1; unsigned char bit07:1; unsigned char bit08:1; unsigned char bit09:1; unsigned char bit10:1; unsigned char bit11:1; unsigned char bit12:1; unsigned char bit13:1; unsigned char bit14:1; unsigned char bit15:1; unsigned char bit16:1; unsigned char bit17:1; unsigned char bit18:1; unsigned char bit19:1; unsigned char bit20:1; unsigned char bit21:1; unsigned char bit22:1; unsigned char bit23:1; unsigned char bit24:1; unsigned char bit25:1; unsigned char bit26:1; unsigned char bit27:1; unsigned char bit28:1; unsigned char bit29:1; unsigned char bit30:1; unsigned char bit31:1; unsigned char bit32:1; }; struct Float *F; F = (struct Float *) &f; printf("\nMSB -->1 bit for sign bit; 8 bit for exponent; 23 bit for mantisa<-- LSB\n"); printf("%d ", F->bit32); printf("%d", F->bit31); printf("%d", F->bit30); printf("%d", F->bit29); printf("%d", F->bit28); printf("%d", F->bit27); printf("%d", F->bit26); printf("%d", F->bit25); printf("%d ", F->bit24); printf("%d", F->bit23); printf("%d", F->bit22); printf("%d", F->bit21); printf("%d", F->bit20); printf("%d", F->bit19); printf("%d", F->bit18); printf("%d", F->bit17); printf("%d", F->bit16); printf("%d", F->bit15); printf("%d", F->bit14); printf("%d", F->bit13); printf("%d", F->bit12); printf("%d", F->bit11); printf("%d", F->bit10); printf("%d", F->bit09); printf("%d", F->bit08); printf("%d", F->bit07); printf("%d", F->bit06); printf("%d", F->bit05); printf("%d", F->bit04); printf("%d", F->bit03); printf("%d", F->bit02); printf("%d\n", F->bit01); }
尝试
union Plop { double value; char data[sizeof(double)]; }; Plop print; print.value = 234.5; std::copy(print.data,print.data+sizeof(double),std::ostream_iterator(std::cout)," "); std::cout << std::endl;
您是否尝试从该地址开始获取d的地址并打印sizeof( d )字节？
使用友好的调试器是查看内存位置值的最佳方法，也就是说，如果您只想查看。
我认为你可以使用移位操作和掩码来“掩盖”实际位。
int t = 128;
for（int i = 0; i <8; ++ i）{printf（“％d”，p＆t）;
p = >> 1;
t = >> 1; }