Re: [libiberty][PATCH] Avoid zero-length VLAs.

[Brooks Moses]

On Mon, Jul 11, 2016 at 4:27 PM, Ian Lance Taylor  wrote:
> On Mon, Jul 11, 2016 at 1:05 PM, Brooks Moses  wrote:
>> Ping?
>
> This is fine, but please add a comment explaining why the code avoids
> 0-length VLAs.  Thanks.

Thanks!

Committed as r238233.  This is the comment I added:

+/* Avoid zero-length VLAs, which are prohibited by the C99 standard
+   and flagged as errors by Address Sanitizer.  */
+__extension__ struct d_saved_scope scopes[(dpi.num_saved_scopes > 0)
+  ? dpi.num_saved_scopes : 1];
+__extension__ struct d_print_template temps[(dpi.num_copy_templates > 0)
+? dpi.num_copy_templates : 1];

- Brooks

Re: [libiberty][PATCH] Avoid zero-length VLAs.

[Ian Lance Taylor]

On Mon, Jul 11, 2016 at 1:05 PM, Brooks Moses  wrote:
> Ping?

This is fine, but please add a comment explaining why the code avoids
0-length VLAs.  Thanks.

Ian

> (I suspect I should have added a libiberty maintainer to cc in the first 
> place.)
>
> On Mon, Jun 13, 2016 at 9:05 AM, Brooks Moses  wrote:
>> Zero-length variable-length-arrays are not allowed in standard C99,
>> and perhaps more importantly, they cause ASAN to complain.  (See,
>> e.g., https://gcc.gnu.org/ml/gcc-patches/2013-09/msg00917.html.)
>>
>> With this patch, the libiberty tests, including demangler-fuzzer, are
>> ASAN-clean.
>>
>> - Brooks
>>
>>
>> 
>>  libiberty/ChangeLog 
>> --- a/libiberty/ChangeLog
>> +++ b/libiberty/ChangeLog
>> @@ -1,3 +1,8 @@
>> +2016-06-12  Brooks Moses  
>> +
>> +   * cp-demangle.c (cplus_demangle_print_callback): Avoid zero-length
>> +   VLAs.
>> +
>>  2016-05-31  Alan Modra  
>>
>> * xmemdup.c (xmemdup): Use xmalloc rather than xcalloc.
>>  libiberty/cp-demangle.c 
>> --- a/libiberty/cp-demangle.c
>> +++ b/libiberty/cp-demangle.c
>> @@ -4120,8 +4120,10 @@
>>
>>{
>>  #ifdef CP_DYNAMIC_ARRAYS
>> -__extension__ struct d_saved_scope scopes[dpi.num_saved_scopes];
>> -__extension__ struct d_print_template temps[dpi.num_copy_templates];
>> +__extension__ struct d_saved_scope scopes[(dpi.num_saved_scopes > 0)
>> + ? dpi.num_saved_scopes : 1];
>> +__extension__ struct d_print_template temps[(dpi.num_copy_templates > 0)
>> +   ? dpi.num_copy_templates : 
>> 1];
>>
>>  dpi.saved_scopes = scopes;
>>  dpi.copy_templates = temps;

Re: [libiberty][PATCH] Avoid zero-length VLAs.

[Brooks Moses]

Ping?

(I suspect I should have added a libiberty maintainer to cc in the first place.)

On Mon, Jun 13, 2016 at 9:05 AM, Brooks Moses  wrote:
> Zero-length variable-length-arrays are not allowed in standard C99,
> and perhaps more importantly, they cause ASAN to complain.  (See,
> e.g., https://gcc.gnu.org/ml/gcc-patches/2013-09/msg00917.html.)
>
> With this patch, the libiberty tests, including demangler-fuzzer, are
> ASAN-clean.
>
> - Brooks
>
>
> 
>  libiberty/ChangeLog 
> --- a/libiberty/ChangeLog
> +++ b/libiberty/ChangeLog
> @@ -1,3 +1,8 @@
> +2016-06-12  Brooks Moses  
> +
> +   * cp-demangle.c (cplus_demangle_print_callback): Avoid zero-length
> +   VLAs.
> +
>  2016-05-31  Alan Modra  
>
> * xmemdup.c (xmemdup): Use xmalloc rather than xcalloc.
>  libiberty/cp-demangle.c 
> --- a/libiberty/cp-demangle.c
> +++ b/libiberty/cp-demangle.c
> @@ -4120,8 +4120,10 @@
>
>{
>  #ifdef CP_DYNAMIC_ARRAYS
> -__extension__ struct d_saved_scope scopes[dpi.num_saved_scopes];
> -__extension__ struct d_print_template temps[dpi.num_copy_templates];
> +__extension__ struct d_saved_scope scopes[(dpi.num_saved_scopes > 0)
> + ? dpi.num_saved_scopes : 1];
> +__extension__ struct d_print_template temps[(dpi.num_copy_templates > 0)
> +   ? dpi.num_copy_templates : 1];
>
>  dpi.saved_scopes = scopes;
>  dpi.copy_templates = temps;

[libiberty][PATCH] Avoid zero-length VLAs.

[Brooks Moses]

Zero-length variable-length-arrays are not allowed in standard C99,
and perhaps more importantly, they cause ASAN to complain.  (See,
e.g., https://gcc.gnu.org/ml/gcc-patches/2013-09/msg00917.html.)

With this patch, the libiberty tests, including demangler-fuzzer, are
ASAN-clean.

- Brooks



 libiberty/ChangeLog 
--- a/libiberty/ChangeLog
+++ b/libiberty/ChangeLog
@@ -1,3 +1,8 @@
+2016-06-12  Brooks Moses  
+
+   * cp-demangle.c (cplus_demangle_print_callback): Avoid zero-length
+   VLAs.
+
 2016-05-31  Alan Modra  

* xmemdup.c (xmemdup): Use xmalloc rather than xcalloc.
 libiberty/cp-demangle.c 
--- a/libiberty/cp-demangle.c
+++ b/libiberty/cp-demangle.c
@@ -4120,8 +4120,10 @@

   {
 #ifdef CP_DYNAMIC_ARRAYS
-__extension__ struct d_saved_scope scopes[dpi.num_saved_scopes];
-__extension__ struct d_print_template temps[dpi.num_copy_templates];
+__extension__ struct d_saved_scope scopes[(dpi.num_saved_scopes > 0)
+ ? dpi.num_saved_scopes : 1];
+__extension__ struct d_print_template temps[(dpi.num_copy_templates > 0)
+   ? dpi.num_copy_templates : 1];

 dpi.saved_scopes = scopes;
 dpi.copy_templates = temps;