Set breakpoint in C or C++ code programmatically for gdb on Linux
C++CLinuxGdbC++ Problem Overview
How can I set a breakpoint in C or C++ code programatically that will work for gdb on Linux?
I.e.:
int main(int argc, char** argv)
{
/* set breakpoint here! */
int a = 3;
a++; /* In gdb> print a; expect result to be 3 */
return 0;
}
C++ Solutions
Solution 1 - C++
One way is to signal an interrupt:
#include <csignal>
// Generate an interrupt
std::raise(SIGINT);
In C:
#include <signal.h>
raise(SIGINT);
UPDATE: MSDN states that Windows doesn't really support SIGINT, so if portability is a concern, you're probably better off using SIGABRT.
Solution 2 - C++
By looking here, I found the following way:
void main(int argc, char** argv)
{
asm("int $3");
int a = 3;
a++; // In gdb> print a; expect result to be 3
}
This seems a touch hackish to me. And I think this only works on x86 architecture.
Solution 3 - C++
In a project I work on, we do this:
raise(SIGABRT); /* To continue from here in GDB: "signal 0". */
(In our case we wanted to crash hard if this happened outside the debugger, generating a crash report if possible. That's one reason we used SIGABRT. Doing this portably across Windows, Mac, and Linux took several attempts. We ended up with a few #ifdefs, helpfully commented here: http://hg.mozilla.org/mozilla-central/file/98fa9c0cff7a/js/src/jsutil.cpp#l66 .)
Solution 4 - C++
Disappointing to see so many answers not using the dedicated signal for software breakpoints, SIGTRAP:
#include <signal.h>
raise(SIGTRAP); // At the location of the BP.
On MSVC/MinGW, you should use DebugBreak, or the __debugbreak intrinsic. A simple #ifdef can handle both cases (POSIX and Win32).
Solution 5 - C++
__asm__("int $3"); should work:
int main(int argc, char** argv)
{
/* set breakpoint here! */
int a = 3;
__asm__("int $3");
a++; /* In gdb> print a; expect result to be 3 */
return 0;
}
Solution 6 - C++
On OS X you can just call std::abort() (it might be the same on Linux)