当使用strlen时，Valgrind报告“使用大小为4的未初始化值”

问题描述

我正在尝试在RaspBerry Pi上使用Valgrind。我正在分析以下程序：

#include <string>
#include <cstring>

int main() {
    std::string blaat = "blaat";
    const char * buf = blaat.c_str();
    size_t l = 0;
    l = strlen(buf);
    printf("string size %u\n",l);
}

编译：

g++ -g -Wall -O0 test.cpp

分析（valgrind-3.16.1）：

valgrind --leak-check=yes ./a.out

结果：

==29572==
==29572== Conditional jump or move depends on uninitialised value(s)
==29572==    at 0x4866210: ??? (in /usr/lib/arm-linux-gnueabihf/libarmmem-v7l.so)
==29572==
==29572== Conditional jump or move depends on uninitialised value(s)
==29572==    at 0x48662DC: ??? (in /usr/lib/arm-linux-gnueabihf/libarmmem-v7l.so)
==29572==
==29572== Use of uninitialised value of size 4
==29572==    at 0x4AABF6C: _itoa_word (_itoa.c:179)
==29572==    by 0x4AB0727: vfprintf (vfprintf.c:1637)
==29572==    by 0x4AB646F: printf (printf.c:33)
==29572==    by 0x1088F: main (test.c:10)
==29572==
==29572== Conditional jump or move depends on uninitialised value(s)
==29572==    at 0x4AABF74: _itoa_word (_itoa.c:179)
==29572==    by 0x4AB0727: vfprintf (vfprintf.c:1637)
==29572==    by 0x4AB646F: printf (printf.c:33)
==29572==    by 0x1088F: main (test.c:10)
==29572==
==29572== Conditional jump or move depends on uninitialised value(s)
==29572==    at 0x4AAF8FC: vfprintf (vfprintf.c:1637)
==29572==    by 0x4AB646F: printf (printf.c:33)
==29572==    by 0x1088F: main (test.c:10)
==29572==
==29572== Conditional jump or move depends on uninitialised value(s)
==29572==    at 0x4AAF99C: vfprintf (vfprintf.c:1637)
==29572==    by 0x4AB646F: printf (printf.c:33)
==29572==    by 0x1088F: main (test.c:10)
==29572==
==29572== Conditional jump or move depends on uninitialised value(s)
==29572==    at 0x4AAFA00: vfprintf (vfprintf.c:1637)
==29572==    by 0x4AB646F: printf (printf.c:33)
==29572==    by 0x1088F: main (test.c:10)
==29572==
==29572== Conditional jump or move depends on uninitialised value(s)
==29572==    at 0x4AAFA7C: vfprintf (vfprintf.c:1637)
==29572==    by 0x4AB646F: printf (printf.c:33)
==29572==    by 0x1088F: main (test.c:10)

一旦我使用“ strlen”，Valgrind就会向我发出有关未初始化值的警告。为什么？

解决方法

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