A little late to the party, so mostly a reminder to me next time I do this search!
I have been able to use:
p/x *(&vec[2])@4
to print 4 elements (as hex) from vec starting at vec[2].
put the following in ~/.gdbinit
define print_vector
if $argc == 2
set $elem = $arg0.size()
if $arg1 >= $arg0.size()
printf "Error, %s.size() = %d, printing last element:\n", "$arg0", $arg0.size()
set $elem = $arg1 -1
end
print *($arg0._M_impl._M_start + $elem)@1
else
print *($arg0._M_impl._M_start)@$arg0.size()
end
end
document print_vector
Display vector contents
Usage: print_vector VECTOR_NAME INDEX
VECTOR_NAME is the name of the vector
INDEX is an optional argument specifying the element to display
end
After restarting gdb (or sourcing ~/.gdbinit), show the associated help like this
gdb) help print_vector
Display vector contents
Usage: print_vector VECTOR_NAME INDEX
VECTOR_NAME is the name of the vector
INDEX is an optional argument specifying the element to display
Example usage:
(gdb) print_vector videoconfig_.entries 0
$32 = {{subChannelId = 177 '\261', sourceId = 0 '\000', hasH264PayloadInfo = false, bitrate = 0, payloadType = 68 'D', maxFs = 0, maxMbps = 0, maxFps = 134, encoder = 0 '\000', temporalLayers = 0 '\000'}}
'Watching' STL containers while debugging is somewhat of a problem. Here are 3 different solutions I have used in the past, none of them is perfect.
1) Use GDB scripts from http://clith.com/gdb_stl_utils/ These scripts allow you to print the contents of almost all STL containers. The problem is that this does not work for nested containers like a stack of sets.
2) Visual Studio 2005 has fantastic support for watching STL containers. This works for nested containers but this is for their implementation for STL only and does not work if you are putting a STL container in a Boost container.
3) Write your own 'print' function (or method) for the specific item you want to print while debugging and use 'call' while in GDB to print the item. Note that if your print function is not being called anywhere in the code g++ will do dead code elimination and the 'print' function will not be found by GDB (you will get a message saying that the function is inlined). So compile with -fkeep-inline-functions
A little late to the party, so mostly a reminder to me next time I do this search!
I have been able to use:
p/x *(&vec[2])@4
to print 4 elements (as hex) from vec starting at vec[2].
With GCC 4.1.2, to print the whole of a std::vector<int> called myVector, do the following:
print *(myVector._M_impl._M_start)@myVector.size()
To print only the first N elements, do:
print *(myVector._M_impl._M_start)@N
Explanation
This is probably heavily dependent on your compiler version, but for GCC 4.1.2, the pointer to the internal array is:
myVector._M_impl._M_start
And the GDB command to print N elements of an array starting at pointer P is:
print P@N
Or, in a short form (for a standard .gdbinit):
p P@N
'Watching' STL containers while debugging is somewhat of a problem. Here are 3 different solutions I have used in the past, none of them is perfect.
1) Use GDB scripts from http://clith.com/gdb_stl_utils/ These scripts allow you to print the contents of almost all STL containers. The problem is that this does not work for nested containers like a stack of sets.
2) Visual Studio 2005 has fantastic support for watching STL containers. This works for nested containers but this is for their implementation for STL only and does not work if you are putting a STL container in a Boost container.
3) Write your own 'print' function (or method) for the specific item you want to print while debugging and use 'call' while in GDB to print the item. Note that if your print function is not being called anywhere in the code g++ will do dead code elimination and the 'print' function will not be found by GDB (you will get a message saying that the function is inlined). So compile with -fkeep-inline-functions
put the following in ~/.gdbinit
define print_vector
if $argc == 2
set $elem = $arg0.size()
if $arg1 >= $arg0.size()
printf "Error, %s.size() = %d, printing last element:\n", "$arg0", $arg0.size()
set $elem = $arg1 -1
end
print *($arg0._M_impl._M_start + $elem)@1
else
print *($arg0._M_impl._M_start)@$arg0.size()
end
end
document print_vector
Display vector contents
Usage: print_vector VECTOR_NAME INDEX
VECTOR_NAME is the name of the vector
INDEX is an optional argument specifying the element to display
end
After restarting gdb (or sourcing ~/.gdbinit), show the associated help like this
gdb) help print_vector
Display vector contents
Usage: print_vector VECTOR_NAME INDEX
VECTOR_NAME is the name of the vector
INDEX is an optional argument specifying the element to display
Example usage:
(gdb) print_vector videoconfig_.entries 0
$32 = {{subChannelId = 177 '\261', sourceId = 0 '\000', hasH264PayloadInfo = false, bitrate = 0, payloadType = 68 'D', maxFs = 0, maxMbps = 0, maxFps = 134, encoder = 0 '\000', temporalLayers = 0 '\000'}}
Source: Stackoverflow.com