[PATCH] Use 1UL constant in order to not overflow (PR c++/89383).

[PATCH] Use 1UL constant in order to not overflow (PR c++/89383).

[Martin Liška]

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Hi.

The patch handles an undefined behavior caused by 1U << 32 shift
for an integer type.

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed?
Thanks,
Martin

libcpp/ChangeLog:

2019-02-18  Martin Liska  <mliska@suse.cz>

	PR c++/89383
	* line-map.c (linemap_line_start): Use 1UL in order
	to not overflow.
---
 libcpp/line-map.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)



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diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index 0e30b4b2b39..284bbd74009 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -745,7 +745,7 @@ linemap_line_start (struct line_maps *set, linenum_type to_line,
 	  || ( /* We can't reuse the map if the line offset is sufficiently
 		  large to cause overflow when computing location_t values.  */
 	      (to_line - ORDINARY_MAP_STARTING_LINE_NUMBER (map))
-	      >= (1U << (CHAR_BIT * sizeof (linenum_type) - column_bits)))
+	      >= (1UL << (CHAR_BIT * sizeof (linenum_type) - column_bits)))
 	  || range_bits < map->m_range_bits)
 	map = linemap_check_ordinary
 	        (const_cast <line_map *>

Re: [PATCH] Use 1UL constant in order to not overflow (PR c++/89383).

[Jakub Jelinek]

On Mon, Feb 18, 2019 at 09:46:33AM +0100, Martin Liška wrote:
> Hi.
> 
> The patch handles an undefined behavior caused by 1U << 32 shift
> for an integer type.

That will still ICE on 32-bit hosts, won't it?
So, either you need ((uint64_t) 1) << ..., or column_bits && ... >= ...

> 2019-02-18  Martin Liska  <mliska@suse.cz>
> 
> 	PR c++/89383
> 	* line-map.c (linemap_line_start): Use 1UL in order
> 	to not overflow.
> ---
>  libcpp/line-map.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> 

> diff --git a/libcpp/line-map.c b/libcpp/line-map.c
> index 0e30b4b2b39..284bbd74009 100644
> --- a/libcpp/line-map.c
> +++ b/libcpp/line-map.c
> @@ -745,7 +745,7 @@ linemap_line_start (struct line_maps *set, linenum_type to_line,
>  	  || ( /* We can't reuse the map if the line offset is sufficiently
>  		  large to cause overflow when computing location_t values.  */
>  	      (to_line - ORDINARY_MAP_STARTING_LINE_NUMBER (map))
> -	      >= (1U << (CHAR_BIT * sizeof (linenum_type) - column_bits)))
> +	      >= (1UL << (CHAR_BIT * sizeof (linenum_type) - column_bits)))
>  	  || range_bits < map->m_range_bits)
>  	map = linemap_check_ordinary
>  	        (const_cast <line_map *>
> 


	Jakub

Re: [PATCH] Use 1UL constant in order to not overflow (PR c++/89383).

[Martin Liška]

On 2/18/19 9:54 AM, Jakub Jelinek wrote:
> On Mon, Feb 18, 2019 at 09:46:33AM +0100, Martin Liška wrote:
>> Hi.
>>
>> The patch handles an undefined behavior caused by 1U << 32 shift
>> for an integer type.
> 
> That will still ICE on 32-bit hosts, won't it?
> So, either you need ((uint64_t) 1) << ..., or column_bits && ... >= ...

Ah, thanks! I'm going to install the former one.

Martin

> 
>> 2019-02-18  Martin Liska  <mliska@suse.cz>
>>
>> 	PR c++/89383
>> 	* line-map.c (linemap_line_start): Use 1UL in order
>> 	to not overflow.
>> ---
>>  libcpp/line-map.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>>
> 
>> diff --git a/libcpp/line-map.c b/libcpp/line-map.c
>> index 0e30b4b2b39..284bbd74009 100644
>> --- a/libcpp/line-map.c
>> +++ b/libcpp/line-map.c
>> @@ -745,7 +745,7 @@ linemap_line_start (struct line_maps *set, linenum_type to_line,
>>  	  || ( /* We can't reuse the map if the line offset is sufficiently
>>  		  large to cause overflow when computing location_t values.  */
>>  	      (to_line - ORDINARY_MAP_STARTING_LINE_NUMBER (map))
>> -	      >= (1U << (CHAR_BIT * sizeof (linenum_type) - column_bits)))
>> +	      >= (1UL << (CHAR_BIT * sizeof (linenum_type) - column_bits)))
>>  	  || range_bits < map->m_range_bits)
>>  	map = linemap_check_ordinary
>>  	        (const_cast <line_map *>
>>
> 
> 
> 	Jakub
>