Last-modified: 2014-12-24 (水) 13:54:35
概要 †
符号拡張についての実験
実験 †
- ソース(test.cpp)
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#include <stdio.h> int main() { signed char sc = 0xff; unsigned char uc = 0xff; printf("signed char\t= %d\t(0x%x)\n", sc, sc); printf("unsigned char\t= %d\t(0x%x)\n", uc, uc); printf("immediate value\t= %d\t(0x%x)\n", 0xff, 0xff); printf("\n"); printf("if (signed char == 0xff)\t\t\t\t-> %s\n", ((sc == 0xff)? "true": "false")); printf("if (signed char == static_cast<signed char>(0xff))\t-> %s\n", ((sc == static_cast<signed char>(0xff))? "true": "false")); printf("if (signed char == static_cast<unsigned char>(0xff))\t-> %s\n", ((sc == static_cast<unsigned char>(0xff))? "true": "false")); printf("\n"); printf("if (unsigned char == 0xff)\t\t\t\t-> %s\n", ((uc == 0xff)? "true": "false")); printf("if (unsigned char == static_cast<signed char>(0xff))\t-> %s\n", ((uc == static_cast<signed char>(0xff))? "true": "false")); printf("if (unsigned char == static_cast<unsigned char>(0xff))\t-> %s\n", ((uc == static_cast<unsigned char>(0xff))? "true": "false")); printf("\n"); return 0; } - 結果
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signed char = -1 (0xffffffff) unsigned char = 255 (0xff) immediate value = 255 (0xff) if (signed char == 0xff) -> false if (signed char == static_cast<signed char>(0xff)) -> true if (signed char == static_cast<unsigned char>(0xff)) -> false if (unsigned char == 0xff) -> true if (unsigned char == static_cast<signed char>(0xff)) -> false if (unsigned char == static_cast<unsigned char>(0xff)) -> true
検証時の環境 †
- Windows 7 Professional x86 SP1
- Visual Studio 2008 SP1
