I would like to view an array of elements pointed to by a pointer. In GDB this can be done by treating the pointed memory as an artificial array of a given length using the operator '#' as
*pointer # length
where length is the number of elements I want to view.
The above syntax does not work in LLDB supplied with Xcode 4.1.
Is there any way how to accomplish the above in LLDB?
There are two ways to do this in lldb.
Most commonly, you use the parray lldb command which takes a COUNT and an EXPRESSION; EXPRESSION is evaluated and should result in a pointer to memory. lldb will then print COUNT items of that type at that address. e.g.
parray 10 ptr
where ptr is of type int *.
Alternatively, it can be done by casting the pointer to a pointer-to-array.
For example, if you have a int* ptr, and you want to view it as an array of ten integers, you can do
p *(int(*)[10])ptr
Because it relies only on standard C features, this method works without any plugins or special settings. It likewise works with other debuggers like GDB or CDB, even though they also have specialized syntaxes for printing arrays.
Starting with the lldb in Xcode 8.0, there is a new built-in parray command. So you can say:
(lldb) parray <COUNT> <EXPRESSION>
to print the memory pointed to by the result of the EXPRESSION as an array of COUNT elements of the type pointed to by the expression.
If the count is stored in a variable available in the current frame, then remember you can do:
(lldb) parray `count_variable` pointer_to_malloced_array
That's a general lldb feature, any command-line argument in lldb surrounded in backticks gets evaluated as an expression that returns an integer, and then the integer gets substituted for the argument before command execution.
The only way I found was via a Python scripting module:
""" File: parray.py """
import lldb
import shlex
def parray(debugger, command, result, dict):
args = shlex.split(command)
va = lldb.frame.FindVariable(args[0])
for i in range(0, int(args[1])):
print va.GetChildAtIndex(i, 0, 1)
Define a command "parray" in lldb:
(lldb) command script import /path/to/parray.py
(lldb) command script add --function parray.parray parray
Now you can use "parray variable length":
(lldb) parray a 5
(double) *a = 0
(double) [1] = 0
(double) [2] = 1.14468
(double) [3] = 2.28936
(double) [4] = 3.43404
With Xcode 4.5.1 (which may or may not help you now), you can do this in the lldb console:
(lldb) type summary add -s "${var[0-63]}" "float *"
(lldb) frame variable pointer
(float *) pointer = 0x000000010ba92950 [0.0,1.0,2.0,3.0, ... ,63.0]
This example assumes that 'pointer' is an array of 64 floats: float pointer[64];
It doesn't seem to be supported yet.
You could use the memory read function (memory read / x), like
(lldb) memory read -ff -c10 `test`
to print a float ten times from that pointer. This should be the same functionality as gdb's #.
Starting with Martin R answer I improved it as follow:
If the pointer is not a simple variable, e.g.:
struct {
int* at;
size_t size;
} a;
Then "parray a.at 5" fails.
I fixed this by replacing "FindVariable" with "GetValueForVariablePath".
Now what if the elements in your array are aggregates, e.g.:
struct {
struct { float x; float y; }* at;
size_t size;
} a;
Then "parray a.at 5" prints: a.at->x, a.at->y, a.at[2], a.at[3], a.at[4] because GetChildAtIndex() returns members of aggregates.
I fixed this by resolving "a.at" + "[" + str(i) + "]" inside the loop instead of resolving "a.at" and then retrieving its children.
Added an optional "first" argument (Usage: parray [FIRST] COUNT), which is useful when you have a huge number of elements.
Made it do the "command script add -f parray.parray parray" at init
Here is my modified version:
import lldb
import shlex
def parray(debugger, command, result, dict):
args = shlex.split(command)
if len(args) == 2:
count = int(args[1])
indices = range(count)
elif len(args) == 3:
first = int(args[1]), count = int(args[2])
indices = range(first, first + count)
else:
print 'Usage: parray ARRAY [FIRST] COUNT'
return
for i in indices:
print lldb.frame.GetValueForVariablePath(args[0] + "[" + str(i) + "]")
def __lldb_init_module(debugger, internal_dict):
debugger.HandleCommand('command script add -f parray.parray parray')
I tried to add a comment but that wasn't great for posting a full answer so I made my own answer. This solves the problem with getting "No Value". You need to get the current frame as I believe lldb.frame is set at module import time so it doesn't have the current frame when you stop at a breakpoint if you load the module from .lldbinit. The other version would work if you import or reloaded the script when you stopped at the breakpoint. The version below should always work.
import lldb
import shlex
#lldb.command('parray', 'command script add -f parray.parray parray')
def parray(debugger, command, result, dict):
target = debugger.GetSelectedTarget()
process = target.GetProcess()
thread = process.GetSelectedThread()
frame = thread.GetSelectedFrame()
args = shlex.split(command)
if len(args) == 2:
count = int(args[1])
indices = range(count)
elif len(args) == 3:
first = int(args[1])
count = int(args[2])
indices = range(first, first + count)
else:
print 'Usage: parray ARRAY [FIRST] COUNT'
return
for i in indices:
print frame.GetValueForVariablePath(args[0] + "[" + str(i) + "]")
To inspect variables you can use the frame variable command (fr v is the shortest unique prefix) which has a -Z flag which does exactly what you want:
(lldb) fr v buffer -Z5
(int64_t *) buffer = 0x000000010950c000 {
(int64_t) [0] = 0
(int64_t) [1] = 0
(int64_t) [2] = 0
(int64_t) [3] = 0
(int64_t) [4] = 0
}
unfortunately expression does not support that flag
Well at that point, you may as well write your own custom C function and invoke it with:
call (int)myprint(args)
Locked. This question and its answers are locked because the question is off-topic but has historical significance. It is not currently accepting new answers or interactions.
(Edit: What is Code Golf: Code Golf are challenges to solve a specific problem with the shortest amount of code by character count in whichever language you prefer. More info here on Meta StackOverflow. )
Code Golfers, here's a challenge on string operations.
Email Address Validation, but without regular expressions (or similar parsing library) of course. It's not so much about the email addresses but how short you can write the different string operations and constraints given below.
The rules are the following (yes, I know, this is not RFC compliant, but these are going to be the 5 rules for this challenge):
At least 1 character out of this group before the #:
A-Z, a-z, 0-9, . (period), _ (underscore)
# has to exist, exactly one time
john#smith.com
^
Period (.) has to exist exactly one time after the #
john#smith.com
^
At least 1 only [A-Z, a-z] character between # and the following . (period)
john#s.com
^
At least 2 only [A-Z, a-z] characters after the final . period
john#smith.ab
^^
Please post the method/function only, which would take a string (proposed email address) and then return a Boolean result (true/false) depending on the email address being valid (true) or invalid (false).
Samples:
b#w.org (valid/true) #w.org (invalid/false)
b#c#d.org (invalid/false) test#org (invalid/false)
test#%.org (invalid/false) s%p#m.org (invalid/false)
j_r#x.c.il (invalid/false) j_r#x.mil (valid/true)
r..t#x.tw (valid/true) foo#a%.com (invalid/false)
Good luck!
C89 (166 characters)
#define B(c)isalnum(c)|c==46|c==95
#define C(x)if(!v|*i++-x)return!1;
#define D(x)for(v=0;x(*i);++i)++v;
v;e(char*i){D(B)C(64)D(isalpha)C(46)D(isalpha)return!*i&v>1;}
Not re-entrant, but can be run multiple times. Test bed:
#include<stdio.h>
#include<assert.h>
main(){
assert(e("b#w.org"));
assert(e("r..t#x.tw"));
assert(e("j_r#x.mil"));
assert(!e("b#c#d.org"));
assert(!e("test#%.org"));
assert(!e("j_r#x.c.il"));
assert(!e("#w.org"));
assert(!e("test#org"));
assert(!e("s%p#m.org"));
assert(!e("foo#a%.com"));
puts("success!");
}
J
:[[/%^(:[[+-/^,&i|:[$[' ']^j+0__:k<3:]]
C89, 175 characters.
#define G &&*((a+=t+1)-1)==
#define H (t=strspn(a,A
t;e(char*a){char A[66]="_.0123456789Aa";short*s=A+12;for(;++s<A+64;)*s=s[-1]+257;return H))G 64&&H+12))G 46&&H+12))>1 G 0;}
I am using the standard library function strspn(), so I feel this answer isn't as "clean" as strager's answer which does without any library functions. (I also stole his idea of declaring a global variable without a type!)
One of the tricks here is that by putting . and _ at the start of the string A, it's possible to include or exclude them easily in a strspn() test: when you want to allow them, use strspn(something, A); when you don't, use strspn(something, A+12). Another is assuming that sizeof (short) == 2 * sizeof (char), and building up the array of valid characters 2 at a time from the "seed" pair Aa. The rest was just looking for a way to force subexpressions to look similar enough that they could be pulled out into #defined macros.
To make this code more "portable" (heh :-P) you can change the array-building code from
char A[66]="_.0123456789Aa";short*s=A+12;for(;++s<A+64;)*s=s[-1]+257;
to
char*A="_.0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
for a cost of 5 additional characters.
Python (181 characters including newlines)
def v(E):
import string as t;a=t.ascii_letters;e=a+"1234567890_.";t=e,e,"#",e,".",a,a,a,a,a,"",a
for c in E:
if c in t[0]:t=t[2:]
elif not c in t[1]:return 0>1
return""==t[0]
Basically just a state machine using obfuscatingly short variable names.
C (166 characters)
#define F(t,u)for(r=s;t=(*s-64?*s-46?isalpha(*s)?3:isdigit(*s)|*s==95?4:0:2:1);++s);if(s-r-1 u)return 0;
V(char*s){char*r;F(2<,<0)F(1=)F(3=,<0)F(2=)F(3=,<1)return 1;}
The single newline is required, and I've counted it as one character.
Python, 149 chars (after putting the whole for loop into one semicolon-separated line, which I haven't done here for "readability" purposes):
def v(s,t=0,o=1):
for c in s:
k=c=="#"
p=c=="."
A=c.isalnum()|p|(c=="_")
L=c.isalpha()
o&=[A,k|A,L,L|p,L,L,L][t]
t+=[1,k,1,p,1,1,0][t]
return(t>5)&o
Test cases, borrowed from strager's answer:
assert v("b#w.org")
assert v("r..t#x.tw")
assert v("j_r#x.mil")
assert not v("b#c#d.org")
assert not v("test#%.org")
assert not v("j_r#x.c.il")
assert not v("#w.org")
assert not v("test#org")
assert not v("s%p#m.org")
assert not v("foo#a%.com")
print "Yeah!"
Explanation: When iterating over the string, two variables keep getting updated.
t keeps the current state:
t = 0: We're at the beginning.
t = 1: We where at the beginning and have found at least one legal character (letter, number, underscore, period)
t = 2: We have found the "#"
t = 3: We have found at least on legal character (i.e. letter) after the "#"
t = 4: We have found the period in the domain name
t = 5: We have found one legal character (letter) after the period
t = 6: We have found at least two legal characters after the period
o as in "okay" starts as 1, i.e. true, and is set to 0 as soon as a character is found that is illegal in the current state.
Legal characters are:
In state 0: letter, number, underscore, period (change state to 1 in any case)
In state 1: letter, number, underscore, period, at-sign (change state to 2 if "#" is found)
In state 2: letter (change state to 3)
In state 3: letter, period (change state to 4 if period found)
In states 4 thru 6: letter (increment state when in 4 or 5)
When we have gone all the way through the string, we return whether t==6 (t>5 is one char less) and o is 1.
Whatever version of C++ MSVC2008 supports.
Here's my humble submission. Now I know why they told me never to do the things I did in here:
#define N return 0
#define I(x) &&*x!='.'&&*x!='_'
bool p(char*a) {
if(!isalnum(a[0])I(a))N;
char*p=a,*b=0,*c=0;
for(int d=0,e=0;*p;p++){
if(*p=='#'){d++;b=p;}
else if(*p=='.'){if(d){e++;c=p;}}
else if(!isalnum(*p)I(p))N;
if (d>1||e>1)N;
}
if(b>c||b+1>=c||c+2>=p)N;
return 1;
}
Not the greatest solution no doubt, and pretty darn verbose, but it is valid.
Fixed (All test cases pass now)
static bool ValidateEmail(string email)
{
var numbers = "1234567890";
var uppercase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var lowercase = uppercase.ToLower();
var arUppercase = uppercase.ToCharArray();
var arLowercase = lowercase.ToCharArray();
var arNumbers = numbers.ToCharArray();
var atPieces = email.Split(new string[] { "#"}, StringSplitOptions.RemoveEmptyEntries);
if (atPieces.Length != 2)
return false;
foreach (var c in atPieces[0])
{
if (!(arNumbers.Contains(c) || arLowercase.Contains(c) || arUppercase.Contains(c) || c == '.' || c == '_'))
return false;
}
if(!atPieces[1].Contains("."))
return false;
var dotPieces = atPieces[1].Split('.');
if (dotPieces.Length != 2)
return false;
foreach (var c in dotPieces[0])
{
if (!(arLowercase.Contains(c) || arUppercase.Contains(c)))
return false;
}
var found = 0;
foreach (var c in dotPieces[1])
{
if ((arLowercase.Contains(c) || arUppercase.Contains(c)))
found++;
else
return false;
}
return found >= 2;
}
C89 character set agnostic (262 characters)
#include <stdio.h>
/* the 'const ' qualifiers should be removed when */
/* counting characters: I don't like warnings :) */
/* also the 'int ' should not be counted. */
/* it needs only 2 spaces (after the returns), should be only 2 lines */
/* that's a total of 262 characters (1 newline, 2 spaces) */
/* code golf starts here */
#include<string.h>
int v(const char*e){
const char*s="0123456789._abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
if(e=strpbrk(e,s))
if(e=strchr(e+1,'#'))
if(!strchr(e+1,'#'))
if(e=strpbrk(e+1,s+12))
if(e=strchr(e+1,'.'))
if(!strchr(e+1,'.'))
if(strlen(e+1)>1)
return 1;
return 0;
}
/* code golf ends here */
int main(void) {
const char *t;
t = "b#w.org"; printf("%s ==> %d\n", t, v(t));
t = "r..t#x.tw"; printf("%s ==> %d\n", t, v(t));
t = "j_r#x.mil"; printf("%s ==> %d\n", t, v(t));
t = "b#c#d.org"; printf("%s ==> %d\n", t, v(t));
t = "test#%.org"; printf("%s ==> %d\n", t, v(t));
t = "j_r#x.c.il"; printf("%s ==> %d\n", t, v(t));
t = "#w.org"; printf("%s ==> %d\n", t, v(t));
t = "test#org"; printf("%s ==> %d\n", t, v(t));
t = "s%p#m.org"; printf("%s ==> %d\n", t, v(t));
t = "foo#a%.com"; printf("%s ==> %d\n", t, v(t));
return 0;
}
Version 2
Still C89 character set agnostic, bugs hopefully corrected (303 chars; 284 without the #include)
#include<string.h>
#define Y strchr
#define X{while(Y
v(char*e){char*s="0123456789_.abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
if(*e!='#')X(s,*e))e++;if(*e++=='#'&&!Y(e,'#')&&Y(e+1,'.'))X(s+12,*e))e++;if(*e++=='.'
&&!Y(e,'.')&&strlen(e)>1){while(*e&&Y(s+12,*e++));if(!*e)return 1;}}}return 0;}
That #define X is absolutely disgusting!
Test as for my first (buggy) version.
VBA/VB6 - 484 chars
Explicit off
usage: VE("b#w.org")
Function V(S, C)
V = True
For I = 1 To Len(S)
If InStr(C, Mid(S, I, 1)) = 0 Then
V = False: Exit For
End If
Next
End Function
Function VE(E)
VE = False
C1 = "abcdefghijklmnopqrstuvwxyzABCDEFGHILKLMNOPQRSTUVWXYZ"
C2 = "0123456789._"
P = Split(E, "#")
If UBound(P) <> 1 Then GoTo X
If Len(P(0)) < 1 Or Not V(P(0), C1 & C2) Then GoTo X
E = P(1): P = Split(E, ".")
If UBound(P) <> 1 Then GoTo X
If Len(P(0)) < 1 Or Not V(P(0), C1) Or Len(P(1)) < 2 Or Not V(P(1), C1) Then GoTo X
VE = True
X:
End Function
Java: 257 chars (not including the 3 end of lines for readability ;-)).
boolean q(char[]s){int a=0,b=0,c=0,d=0,e=0,f=0,g,y=-99;for(int i:s)
d=(g="#._0123456789QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm".indexOf(i))<0?
y:g<1&&++e>0&(b<1|++a>1)?y:g==1&e>0&(c<1||f++>0)?y:++b>0&g>12?f>0?d+1:f<1&e>0&&++c>0?
d:d:d;return d>1;}
Passes all the tests (my older version was incorrect).
Erlang 266 chars:
-module(cg_email).
-export([test/0]).
%%% golf code begin %%%
-define(E,when X>=$a,X=<$z;X>=$A,X=<$Z).
-define(I(Y,Z),Y([X|L])?E->Z(L);Y(_)->false).
-define(L(Y,Z),Y([X|L])?E;X>=$0,X=<$9;X=:=$.;X=:=$_->Z(L);Y(_)->false).
?L(e,m).
m([$#|L])->a(L);?L(m,m).
?I(a,i).
i([$.|L])->l(L);?I(i,i).
?I(l,c).
?I(c,g).
g([])->true;?I(g,g).
%%% golf code end %%%
test() ->
true = e("b#w.org"),
false = e("b#c#d.org"),
false = e("test#%.org"),
false = e("j_r#x.c.il"),
true = e("r..t#x.tw"),
false = e("test#org"),
false = e("s%p#m.org"),
true = e("j_r#x.mil"),
false = e("foo#a%.com"),
ok.
Ruby, 225 chars.
This is my first Ruby program, so it's probably not very Ruby-like :-)
def v z;r=!a=b=c=d=e=f=0;z.chars{|x|case x when'#';r||=b<1||!e;e=!1 when'.'
e ?b+=1:(a+=1;f=e);r||=a>1||(c<1&&!e)when'0'..'9';b+=1;r|=!e when'A'..'Z','a'..'z'
e ?b+=1:f ?c+=1:d+=1;else r=1 if x!='_'||!e|!b+=1;end};!r&&d>1 end
'Using no regex':
PHP 47 Chars.
<?=filter_var($argv[1],FILTER_VALIDATE_EMAIL);
Haskell (GHC 6.8.2), 165 161 144C Characters
Using pattern matching, elem, span and all:
a=['A'..'Z']++['a'..'z']
e=f.span(`elem`"._0123456789"++a)
f(_:_,'#':d)=g$span(`elem`a)d
f _=False
g(_:_,'.':t#(_:_:_))=all(`elem`a)t
g _=False
The above was tested with the following code:
main :: IO ()
main = print $ and [
e "b#w.org",
e "r..t#x.tw",
e "j_r#x.mil",
not $ e "b#c#d.org",
not $ e "test#%.org",
not $ e "j_r#x.c.il",
not $ e "#w.org",
not $ e "test#org",
not $ e "s%p#m.org",
not $ e "foo#a%.com"
]