How do I set a conditional breakpoint in gdb, when char* x points to a string whose value equals "hello"?

Can I specify that I want gdb to break at line x when `char* x` points to a string whose value equals `"hello"`? If yes, how?

You can use `strcmp`:

break x:20 if strcmp(y, "hello") == 0

`20` is line number, `x` can be any filename and `y` can be any variable.

break x if ((int)strcmp(y, "hello")) == 0

On some implementations gdb might not know the return type of strcmp. That means you would have to cast, otherwise it would always evaluate to true!

Use a [break condition](

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) with `$_streq` (one of GDB's own [convenience functions](

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"current convenience functions online documentation")):
```gdb
break [where] if $_streq(x, "hello")
```
or, if your breakpoint already exists, add the condition to it:
```gdb
condition <breakpoint number> $_streq(x, "hello")
```

[Since GDB 7.5 (long ago)](

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"git commit, released 2012-08-17") you can use that and a handful of other native [convenience functions](

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"current online documentation") for various string matching, including `$_regex` which supports the [Python regex syntax](

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):
```gdb
$_memeq(buf1, buf2, length)
$_regex(str, regex)
$_streq(str1, str2)
$_strlen(str)
```

These are quite less problematic than having to execute the usual `strcmp()` injected to the process' stack, because that can have undesired side effects.

Alas, using the native functions is not always possible, because they rely on GDB being compiled with Python support. This is usually the default, but some constrained environments might not have it. To be sure, you can check it by running `show configuration` inside GDB and searching for `--with-python`. This shell oneliner does the trick, too:
```sh
gdb -n -quiet -batch -ex 'show configuration' | grep 'with-python'
```