Une collection de notes diverses sur des trucs et astuces pour faire des choses avec un ordinateur...
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\chapter{Debug}\index{Debug}
\label{chap:debug}
Quand plus rien ne marche, il existe encore un espoir...
\section{strace}\index{strace}
\section{LD\_PRELOAD}\index{LD\_PRELOAD}
\begin{lstlisting}[language=C]
/*
spy_getenv.so: spy_getenv.c Makefile
gcc -Wall -shared -fPIC $< -ldl -o $@
*/
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#define __USE_GNU
#include <dlfcn.h>
typedef char * (*original_getenv)(const char *envname);
char *getenv(char *envname)
{
static char *arrow = "--getenv--> ";
static char *wtf = " --> WTF ?";
char *content;
original_getenv orig_getenv;
orig_getenv = (original_getenv)dlsym(RTLD_NEXT, "getenv");
write(STDERR_FILENO, arrow, strlen(arrow));
write(STDERR_FILENO, envname, strlen(envname));
content = orig_getenv(envname);
if (NULL != content) {
write(STDERR_FILENO, "=", 1);
write(STDERR_FILENO, content, strlen(content));
}
else {
write(STDERR_FILENO, wtf, strlen(wtf));
}
write(STDERR_FILENO, "\n", 1);
return content;
}
\end{lstlisting}