Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>As far as I know, there is not built-in support for this kind of thing. Usually a library would publish a probe that decodes the string for you (as Brad mentions). So since in your case you can't modify the library, you'll need to use the <code>pid</code> provider and hook into a user function, and decode it yourself.</p> <p>The solution (which is very similar to the approach you would use in C++ to dump a <code>std::string</code>) is to dump out the pointer which is stored at an 2 word offset from the base <code>CFStringRef</code> pointer. Note that since a <code>CFString</code> can store strings internally in a variety of formats and representations, this is subject to change.</p> <p>Given the trivial test application:</p> <pre><code>#include &lt;CoreFoundation/CoreFoundation.h&gt; int mungeString(CFStringRef someString) { const char* str = CFStringGetCStringPtr(someString, kCFStringEncodingMacRoman); if (str) return strlen(str); else return 0; } int main(int argc, char* argv[]) { CFStringRef data = CFSTR("My test data"); printf("%u\n", mungeString(data)); return 0; } </code></pre> <p>The following <code>dtrace</code> script will print the string value of the first argument, assuming it is a <code>CFStringRef</code>:</p> <pre><code>#!/usr/sbin/dtrace -s /* Dumps a CFStringRef parameter to a function, assuming MacRoman or ASCII encoding. The C-style string is found at an offset of 2 words past the CFStringRef pointer. This appears to work in 10.6 in 32- and 64-bit binaries, but is an implementation detail that is subject to change. Written by Gavin Baker &lt;gavinb.antonym.org&gt; */ #pragma D option quiet /* Uncomment for LP32 */ /* typedef long ptr_t; */ /* Uncomment for LP64 */ typedef long long ptr_t; pid$target::mungeString:entry { printf("Called mungeString:\n"); printf("arg0 = 0x%p\n",arg0); this-&gt;str = *(ptr_t*)copyin(arg0+2*sizeof(ptr_t), sizeof(ptr_t)); printf("string addr = %p\n", this-&gt;str); printf("string val = %s\n", copyinstr(this-&gt;str)); } </code></pre> <p>And the output will be something like:</p> <pre><code>$ sudo dtrace -s dump.d -c ./build/Debug/dtcftest 12 Called mungeString: arg0 = 0x2030 string addr = 1fef string val = My test data </code></pre> <p>Simply uncomment the right <code>typedef</code> depending on whether you are running against a 32-bit or 64-bit binary. I have tested this against both architectures on 10.6 and it works fine.</p>
    singulars
    1. This table or related slice is empty.
    1. POHow do I print a CFStringRef in a DTrace action?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USgavinb
    1. USgavinb
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POHow do I print a CFStringRef in a DTrace action?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COUsing this program and this probe file, I just get a big list of this: dtrace: error on enabled probe ID 1 (ID 93815: pid11402:sc:mungeString:entry): invalid address (0x7c8) in action #5 at DIF offset 12 Taking out the line that prints the string, I see that all the string addrs are a tad unusual: Called mungeString: arg0 = 0x100001068 string addr = 7c8 Adding a second, different constant string and mungeString'ing it, I get the same string addr for both strings.
      singulars
      1. PO
      1. USTALlama
    2. COOk, I can tell from the memory addresses that you must be using 10.6 and building a 64-bit app. I wrote the test app (in a hurry!) on 10.5 as it was all I had access to at the time. I should have used sizeof(intptr_t) for the offset in the DTrace script to be arch-neutral (rather than hardcode 8, which would now be 16 in a 64-bit app). I'll have a look on a 10.6 machine.
      singulars
      1. PO
      1. USgavinb
    3. CO@TALlama Please try the updated script above. I tested it on both 32-bit and 64-bit binaries and it works fine.
      singulars
      1. PO
      1. USgavinb
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload