llvm dev - Aug 2011 - [LLVMdev] [llvm-commits] [polly] r138203 - /polly/trunk/lib/Support/GICHelper.cpp

> -  std::string string(isl_printer_get_str(p));
> +  char *char_str = isl_printer_get_str(p);
> +  std::string string(char_str);
> +  free(char_str);
This got me wondering: If this were compiled with exceptions it
wouldn't be safe (std::string's ctor could throw & then the free
wouldn't be called), but I know LLVM doesn't use exceptions in its
codebase.

Are exceptions actually disabled in the build? (I assume so)
How are memory allocation failures handled?
How do the standard library types function in the absence of
exceptions? (I've seen Howard Hinnant checking in changes to libc++ to
support cases where exceptions are disabled & I was wondering what
sort of semantics he (& libstdc++ too) provide when exceptions are
disabled).

- David

On 08/20/2011 06:15 PM, David Blaikie wrote:
>> -  std::string string(isl_printer_get_str(p));
>> +  char *char_str = isl_printer_get_str(p);
>> +  std::string string(char_str);
>> +  free(char_str);
>
> This got me wondering: If this were compiled with exceptions it
> wouldn't be safe (std::string's ctor could throw&  then the
free
> wouldn't be called), but I know LLVM doesn't use exceptions in its
> codebase.
You are right. Even though it would not yield to unexpected behavior, we 
would have a memory leak.
> Are exceptions actually disabled in the build? (I assume so)
At least my build uses -fno-exceptions
> How are memory allocation failures handled?
Interesting question. I must admit in this code they are not handled at 
all. I would be very interested in how other people would handle this.
> How do the standard library types function in the absence of
> exceptions? (I've seen Howard Hinnant checking in changes to libc++ to
> support cases where exceptions are disabled&  I was wondering what
> sort of semantics he (&  libstdc++ too) provide when exceptions are
> disabled).
Again a very interesting question. I assume for explicit allocations 
with 'new' libstdc++ would return a NULL pointer (instead of throwing an
exception).

str::string *str = new std::string("Hallo");

However, I have no idea what happens in the case of:

str::string str("Hallo);

Tobi