Can print stack trace in catch? #346
Comments
|
You would have to collect the function pointer/stack trace at the location
where the error is produced (in do_something). Then you can print it
within the catch handler.
…On Thu, Jan 9, 2025, 10:58 K-KaUI ***@***.***> wrote:
In a try block, several functions are called (which may come from
third-party libraries). To ensure the system runs properly, exceptions
thrown by these functions need to be caught. When an exception is caught,
the call stack should be printed to help with troubleshooting, just like in
the following Python example.
I understand that due to the stack unwinding issue in the C++ exception
mechanism, it seems difficult to implement something similar to Python or
other languages where the exception stack is printed in the catch block.
Does backward-cpp support this feature? Or is there another way to achieve
this?
import traceback
def do_something():
raise Exception("throw exception from third-party library")
def test1():
print("test1 ok")
def test2():
do_something()
def test3():
print("test3 ok")
if __name__ == '__main__':
try:
test1()
test2()
test3()
except Exception as e:
print(e)
traceback.print_exc()
print("do something else")
python test_exception.py test1 okthrow exception from third-party libraryTraceback (most recent call last):
File "test_exception.py", line 18, in <module>
test2()
File "test_exception.py", line 10, in test2
do_something()
File "test_exception.py", line 4, in do_something
raise Exception("throw exception from third-party library")Exception: throw exception from third-party librarydo something else
When using backward-cpp without exception handling, the program crashes
and correctly prints the stack trace. However, when an exception is caught,
it does nothing and does not print the stack trace.
#define BACKWARD_HAS_BFD 1
#include <iostream>
#include <exception>
#include <stdexcept>
#include "backward.hpp"
backward::SignalHandling sh{};void do_something() {
throw std::runtime_error("throw exception from third-party library");
}void test1() {
std::cout << "test1 ok" << std::endl;
}void test2() {
do_something();
}void test3() {
std::cout << "test3 ok" << std::endl;
}int main() {
// try {
test1();
test2();
test3();
// } catch (const std::exception& e) {
// std::cout << e.what() << std::endl;
// std::cout << "Exception caught: " << e.what() << std::endl;
// }
std::cout << "do something else" << std::endl;
return 0;
}
./test_exception
test1 ok
terminate called after throwing an instance of 'std::runtime_error'
what(): throw exception from third-party library
Stack trace (most recent call last):
#10 Object "", at 0xffffffffffffffff, in
#9 Object "build/test_exception", at 0x55e45ba55fcd, in _start
BFD: DWARF error: section .debug_info is larger than its filesize! (0x93f189 vs 0x531098)
#8 Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f40ba673082, in __libc_start_main
#7 | Source "test/test_exception.cpp", line 22, in main
| 20: // try {
| 21: test1();
| > 22: test2();
| 23: test3();
| 24: // } catch (const std::exception& e) {
Source "test/test_exception.cpp", line 14, in test2() [0x55e45ba55e1d]
11: std::cout << "test1 ok" << std::endl;
12: }
13: void test2() {
> 14: do_something();
15: }
16: void test3() {
17: std::cout << "test3 ok" << std::endl;
#6 Source "test/test_exception.cpp", line 8, in do_something() [0x55e45ba560e7]
5: #include "backward.hpp"
6: backward::SignalHandling sh{};
7: void do_something() {
> 8: throw std::runtime_error("throw exception from third-party library");
9: }
10: void test1() {
11: std::cout << "test1 ok" << std::endl;
#5 Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7f40baa55698, in __cxa_throw
#4 Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7f40baa553e6, in std::terminate()
#3 Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7f40baa5537b, in std::rethrow_exception(std::__exception_ptr::exception_ptr)
#2 Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7f40baa498d0, in __cxa_throw_bad_array_new_length
#1 Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f40ba671858, in abort
#0 Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f40ba69200b, in gsignalAborted (Signal sent by tkill() 168610 1000)Aborted (core dumped)
#define BACKWARD_HAS_BFD 1
#include <iostream>
#include <exception>
#include <stdexcept>
#include "backward.hpp"
backward::SignalHandling sh{};void do_something() {
throw std::runtime_error("throw exception from third-party library");
}void test1() {
std::cout << "test1 ok" << std::endl;
}void test2() {
do_something();
}void test3() {
std::cout << "test3 ok" << std::endl;
}int main() {
try {
test1();
test2();
test3();
} catch (const std::exception& e) {
std::cout << e.what() << std::endl;
std::cout << "Exception caught: " << e.what() << std::endl;
}
std::cout << "do something else" << std::endl;
return 0;
}
./test_exception
test1 okthrow exception from third-party library
Exception caught: throw exception from third-party librarydo something else
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Thank you for your reply. do_something simulates an exception thrown by a third-party library, and I don't have the ability to collect function pointers/stack trace within it. |
|
I don't think C++ embed the source (code pointer) of exceptions. C++ walks
the stack up to find a catch handler. If it doesn't find any, then it
ultimately raises a signal, with the source (code pointer) of the
exception. Hence why you can print it in your test. But when a catch
handler is found, I don't think this code pointer is kept around. I do
recall C++11 (or 17?) added some functions to manipulate exceptions (for
example to capture and re throw across threads etc). I wonder if there is
something there to explore.
…On Thu, Jan 9, 2025, 11:38 K-KaUI ***@***.***> wrote:
You would have to collect the function pointer/stack trace at the location
where the error is produced (in do_something). Then you can print it within
the catch handler.
… <#m_-6938620540204400117_>
On Thu, Jan 9, 2025, 10:58 K-KaUI *@*.*> wrote: In a try block, several
functions are called (which may come from third-party libraries). To ensure
the system runs properly, exceptions thrown by these functions need to be
caught. When an exception is caught, the call stack should be printed to
help with troubleshooting, just like in the following Python example. I
understand that due to the stack unwinding issue in the C++ exception
mechanism, it seems difficult to implement something similar to Python or
other languages where the exception stack is printed in the catch block.
Does backward-cpp support this feature? Or is there another way to achieve
this? import traceback def do_something(): raise Exception("throw exception
from third-party library") def test1(): print("test1 ok") def test2():
do_something() def test3(): print("test3 ok") if name == 'main': try:
test1() test2() test3() except Exception as e: print(e)
traceback.print_exc() print("do something else") python test_exception.py
test1 okthrow exception from third-party libraryTraceback (most recent call
last): File "test_exception.py", line 18, in test2() File
"test_exception.py", line 10, in test2 do_something() File
"test_exception.py", line 4, in do_something raise Exception("throw
exception from third-party library")Exception: throw exception from
third-party librarydo something else When using backward-cpp without
exception handling, the program crashes and correctly prints the stack
trace. However, when an exception is caught, it does nothing and does not
print the stack trace. #define BACKWARD_HAS_BFD 1 #include #include
#include #include "backward.hpp" backward::SignalHandling sh{};void
do_something() { throw std::runtime_error("throw exception from third-party
library"); }void test1() { std::cout << "test1 ok" << std::endl; }void
test2() { do_something(); }void test3() { std::cout << "test3 ok" <<
std::endl; }int main() { // try { test1(); test2(); test3(); // } catch
(const std::exception& e) { // std::cout << e.what() << std::endl; //
std::cout << "Exception caught: " << e.what() << std::endl; // } std::cout
<< "do something else" << std::endl; return 0; } ./test_exception test1 ok
terminate called after throwing an instance of 'std::runtime_error' what():
throw exception from third-party library Stack trace (most recent call
last): #10 <#10> Object "", at
0xffffffffffffffff, in #9 <#9>
Object "build/test_exception", at 0x55e45ba55fcd, in _start BFD: DWARF
error: section .debug_info is larger than its filesize! (0x93f189 vs
0x531098) #8 <#8> Object
"/lib/x86_64-linux-gnu/libc.so.6", at 0x7f40ba673082, in __libc_start_main
#7 <#7> | Source
"test/test_exception.cpp", line 22, in main | 20: // try { | 21: test1(); |
> 22: test2(); | 23: test3(); | 24: // } catch (const std::exception& e) {
Source "test/test_exception.cpp", line 14, in test2() [0x55e45ba55e1d] 11:
std::cout << "test1 ok" << std::endl; 12: } 13: void test2() { > 14:
do_something(); 15: } 16: void test3() { 17: std::cout << "test3 ok" <<
std::endl; #6 <#6> Source
"test/test_exception.cpp", line 8, in do_something() [0x55e45ba560e7] 5:
#include "backward.hpp" 6: backward::SignalHandling sh{}; 7: void
do_something() { > 8: throw std::runtime_error("throw exception from
third-party library"); 9: } 10: void test1() { 11: std::cout << "test1 ok"
<< std::endl; #5 <#5> Object
"/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7f40baa55698, in __cxa_throw
#4 <#4> Object
"/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7f40baa553e6, in
std::terminate() #3 <#3> Object
"/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7f40baa5537b, in
std::rethrow_exception(std::__exception_ptr::exception_ptr) #2
<#2> Object
"/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7f40baa498d0, in
__cxa_throw_bad_array_new_length #1
<#1> Object
"/lib/x86_64-linux-gnu/libc.so.6", at 0x7f40ba671858, in abort #0 Object
"/lib/x86_64-linux-gnu/libc.so.6", at 0x7f40ba69200b, in gsignalAborted
(Signal sent by tkill() 168610 1000)Aborted (core dumped) #define
BACKWARD_HAS_BFD 1 #include #include #include #include "backward.hpp"
backward::SignalHandling sh{};void do_something() { throw
std::runtime_error("throw exception from third-party library"); }void
test1() { std::cout << "test1 ok" << std::endl; }void test2() {
do_something(); }void test3() { std::cout << "test3 ok" << std::endl; }int
main() { try { test1(); test2(); test3(); } catch (const std::exception& e)
{ std::cout << e.what() << std::endl; std::cout << "Exception caught: " <<
e.what() << std::endl; } std::cout << "do something else" << std::endl;
return 0; } ./test_exception test1 okthrow exception from third-party
library Exception caught: throw exception from third-party librarydo
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Thank you for your reply. do_something simulates an exception thrown by a
third-party library, and I don't have the ability to collect function
pointers/stack trace within it.
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Thanks, I'll keep exploring. |
Hi,
In a try block, several functions are called (which may come from third-party libraries). To ensure the system runs properly, exceptions thrown by these functions need to be caught. When an exception is caught, the call stack should be printed to help with troubleshooting, just like in the following Python example.
I understand that due to the stack unwinding issue in the C++ exception mechanism, it seems difficult to implement something similar to Python or other languages where the exception stack is printed in the catch block. Does backward-cpp support this feature? Or is there another way to achieve this?
When using backward-cpp without exception handling, the program crashes and correctly prints the stack trace. However, when an exception is caught, it does nothing and does not print the stack trace.
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