ffix required

ffix required

[Alejandro Colomar]

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Hi Florian,

I was testing my regex-based program for finding C source code, and 
accidentally found some incorrectly indented braces in glibc that broke 
my regex.

In the code below, see how it finds two consecutive structures (the 
first one incorrectly), due to the regex trying to find opening and 
closing braces with the same indentation level.

It may be good to check if this happens elsewhere too.

Cheers,

Alex


$ grepc ucontext_t ./sysdeps/unix/sysv/linux/x86/sys/ucontext.h
./sysdeps/unix/sysv/linux/x86/sys/ucontext.h:133:
typedef struct
   {
     gregset_t __ctx(gregs);
     /* Note that fpregs is a pointer.  */
     fpregset_t __ctx(fpregs);
     __extension__ unsigned long long __reserved1 [8];
} mcontext_t;

/* Userlevel context.  */
typedef struct ucontext_t
   {
     unsigned long int __ctx(uc_flags);
     struct ucontext_t *uc_link;
     stack_t uc_stack;
     mcontext_t uc_mcontext;
     sigset_t uc_sigmask;
     struct _libc_fpstate __fpregs_mem;
     __extension__ unsigned long long int __ssp[4];
   } ucontext_t;


./sysdeps/unix/sysv/linux/x86/sys/ucontext.h:247:
typedef struct ucontext_t
   {
     unsigned long int __ctx(uc_flags);
     struct ucontext_t *uc_link;
     stack_t uc_stack;
     mcontext_t uc_mcontext;
     sigset_t uc_sigmask;
     struct _libc_fpstate __fpregs_mem;
     unsigned long int __ssp[4];
   } ucontext_t;


-- 
Alejandro Colomar
<http://www.alejandro-colomar.es/>

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Re: ffix required

[Florian Weimer]

* Alejandro Colomar:

> $ grepc ucontext_t ./sysdeps/unix/sysv/linux/x86/sys/ucontext.h
> ./sysdeps/unix/sysv/linux/x86/sys/ucontext.h:133:
> typedef struct
>   {
>     gregset_t __ctx(gregs);
>     /* Note that fpregs is a pointer.  */
>     fpregset_t __ctx(fpregs);
>     __extension__ unsigned long long __reserved1 [8];
> } mcontext_t;

What would you do if this turned into this?

typedef struct {
    gregset_t __ctx(gregs);
    /* Note that fpregs is a pointer.  */
    fpregset_t __ctx(fpregs);
    __extension__ unsigned long long __reserved1 [8];
} mcontext_t;

It's probably not how we'd fix this (it's not really GNU style), but
other projects might use that.

Thanks,
Florian

Re: ffix required

[Alejandro Colomar]

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Hi, Florian!

On 5/25/22 14:01, Florian Weimer wrote:
> * Alejandro Colomar:
> 
>> $ grepc ucontext_t ./sysdeps/unix/sysv/linux/x86/sys/ucontext.h
>> ./sysdeps/unix/sysv/linux/x86/sys/ucontext.h:133:
>> typedef struct
>>    {
>>      gregset_t __ctx(gregs);
>>      /* Note that fpregs is a pointer.  */
>>      fpregset_t __ctx(fpregs);
>>      __extension__ unsigned long long __reserved1 [8];
>> } mcontext_t;
> 
> What would you do if this turned into this?
> 
> typedef struct {
>      gregset_t __ctx(gregs);
>      /* Note that fpregs is a pointer.  */
>      fpregset_t __ctx(fpregs);
>      __extension__ unsigned long long __reserved1 [8];
> } mcontext_t;

That is covered.  The regex is:

'(?s)^[ \t]*typedef\s+(struct|union|enum)\b(?:(?!\W'"$1"'\W)([\w 
\t[\]]|::))*\n*([ \t]*){(?:(?!^\3?}).)*?^\3}\s*'"$1"'(\[[\w\(,\)]\])*;'

with the relevant part being '\n*([ \t]*){(?:(?!^\3?}).)*?^\3}'

'\3', which resolves to '([ \t]*)' is empty when the opening brace is in 
the same line as '(struct|union|enum)'.  So, if the opening brace is in 
the same line, the closing brace must have no leading whitespace for 
this regex to work.

You can find the full program source code here, if you're 
curious/interested (it's a small sh(1) script):

<http://www.alejandro-colomar.es/src/alx/alx/grepc.git/tree/bin/grepc>
<git://www.alejandro-colomar.es/src/alx/alx/grepc.git>

> 
> It's probably not how we'd fix this (it's not really GNU style), but
> other projects might use that.

The regex isn't perfect, and probably there's no perfect regex for 
searching C code, but I support "sane" coding standards (or I attempt to).

The only widely-used (although luckily not so much these days) style 
that I'm aware that my regexes can't find is K&R-style function 
definitions, i.e.:

foo(int, long)
     int x;
     long y;
{
     return x;
}

But I can live with it.


Cheers,

Alex


-- 
Alejandro Colomar
<http://www.alejandro-colomar.es/>

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