[PATCH] [gdb/tdep] Eliminate ostringstream use from arc_check_tdesc_feature

[PATCH] [gdb/tdep] Eliminate ostringstream use from arc_check_tdesc_feature

[Tom de Vries]

We generally avoid C++ streams in GDB sources [1].

Remove an instance of std::ostringstream in arc_check_tdesc_feature.

While we're at it, fix an array index bug:
...
-		reg_names << " or '" << reg.names[0] << "'";
+		string_appendf (reg_names, " or '%s'", reg.names[i]);
...

Tested on x86_64-linux, using a trigger patch:
...
-      if (!found && reg.required_p)
+      if (true || (!found && reg.required_p))
...
and doing "maint selftest" and observing the output:
...
Running selftest unpack_field_as_long::ARC600.
Error: Cannot find required register(s) 'r0' in feature 'org.gnu.gdb.arc.core'.
Error: Cannot find required register(s) 'pc' in feature 'org.gnu.gdb.arc.aux'.
...

[1] https://sourceware.org/pipermail/gdb-patches/2026-March/226117.html
---
 gdb/arc-tdep.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/gdb/arc-tdep.c b/gdb/arc-tdep.c
index ff283014e52..4936a5c8fbb 100644
--- a/gdb/arc-tdep.c
+++ b/gdb/arc-tdep.c
@@ -44,7 +44,6 @@
 
 /* Standard headers.  */
 #include <algorithm>
-#include <sstream>
 
 /* The frame unwind cache for ARC.  */
 
@@ -2100,16 +2099,16 @@ arc_check_tdesc_feature (struct tdesc_arch_data *tdesc_data,
 
       if (!found && reg.required_p)
 	{
-	  std::ostringstream reg_names;
+	  std::string reg_names;
 	  for (std::size_t i = 0; i < reg.names.size(); ++i)
 	    {
 	      if (i == 0)
-		reg_names << "'" << reg.names[0] << "'";
+		string_appendf (reg_names, "'%s'", reg.names[0]);
 	      else
-		reg_names << " or '" << reg.names[0] << "'";
+		string_appendf (reg_names, " or '%s'", reg.names[i]);
 	    }
 	  arc_print (_("Error: Cannot find required register(s) %s "
-		       "in feature '%s'.\n"), reg_names.str ().c_str (),
+		       "in feature '%s'.\n"), reg_names.c_str (),
 		       feature->name.c_str ());
 	  return false;
 	}

base-commit: d1cb5bd656a253cd69dbcd096f21f658cda697c7
-- 
2.51.0

Re: [PATCH] [gdb/tdep] Eliminate ostringstream use from arc_check_tdesc_feature

[Simon Marchi]

On 3/22/26 2:58 AM, Tom de Vries wrote:
> We generally avoid C++ streams in GDB sources [1].
> 
> Remove an instance of std::ostringstream in arc_check_tdesc_feature.
> 
> While we're at it, fix an array index bug:
> ...
> -		reg_names << " or '" << reg.names[0] << "'";
> +		string_appendf (reg_names, " or '%s'", reg.names[i]);
> ...
> 
> Tested on x86_64-linux, using a trigger patch:
> ...
> -      if (!found && reg.required_p)
> +      if (true || (!found && reg.required_p))
> ...
> and doing "maint selftest" and observing the output:
> ...
> Running selftest unpack_field_as_long::ARC600.
> Error: Cannot find required register(s) 'r0' in feature 'org.gnu.gdb.arc.core'.
> Error: Cannot find required register(s) 'pc' in feature 'org.gnu.gdb.arc.aux'.
> ...
> 
> [1] https://sourceware.org/pipermail/gdb-patches/2026-March/226117.html
> ---
>  gdb/arc-tdep.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/gdb/arc-tdep.c b/gdb/arc-tdep.c
> index ff283014e52..4936a5c8fbb 100644
> --- a/gdb/arc-tdep.c
> +++ b/gdb/arc-tdep.c
> @@ -44,7 +44,6 @@
>  
>  /* Standard headers.  */
>  #include <algorithm>
> -#include <sstream>
>  
>  /* The frame unwind cache for ARC.  */
>  
> @@ -2100,16 +2099,16 @@ arc_check_tdesc_feature (struct tdesc_arch_data *tdesc_data,
>  
>        if (!found && reg.required_p)
>  	{
> -	  std::ostringstream reg_names;
> +	  std::string reg_names;
>  	  for (std::size_t i = 0; i < reg.names.size(); ++i)
>  	    {
>  	      if (i == 0)
> -		reg_names << "'" << reg.names[0] << "'";
> +		string_appendf (reg_names, "'%s'", reg.names[0]);
>  	      else
> -		reg_names << " or '" << reg.names[0] << "'";
> +		string_appendf (reg_names, " or '%s'", reg.names[i]);

Looks like you fixed a bug here (0 -> i).

Approved-By: Simon Marchi <simon.marchi@efficios.com>

Simon

Re: [PATCH] [gdb/tdep] Eliminate ostringstream use from arc_check_tdesc_feature

[Tom de Vries]

On 3/22/26 3:41 PM, Simon Marchi wrote:
> On 3/22/26 2:58 AM, Tom de Vries wrote:
>> We generally avoid C++ streams in GDB sources [1].
>>
>> Remove an instance of std::ostringstream in arc_check_tdesc_feature.
>>
>> While we're at it, fix an array index bug:
>> ...
>> -		reg_names << " or '" << reg.names[0] << "'";
>> +		string_appendf (reg_names, " or '%s'", reg.names[i]);
>> ...
>>
>> Tested on x86_64-linux, using a trigger patch:
>> ...
>> -      if (!found && reg.required_p)
>> +      if (true || (!found && reg.required_p))
>> ...
>> and doing "maint selftest" and observing the output:
>> ...
>> Running selftest unpack_field_as_long::ARC600.
>> Error: Cannot find required register(s) 'r0' in feature 'org.gnu.gdb.arc.core'.
>> Error: Cannot find required register(s) 'pc' in feature 'org.gnu.gdb.arc.aux'.
>> ...
>>
>> [1] https://sourceware.org/pipermail/gdb-patches/2026-March/226117.html
>> ---
>>   gdb/arc-tdep.c | 9 ++++-----
>>   1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/gdb/arc-tdep.c b/gdb/arc-tdep.c
>> index ff283014e52..4936a5c8fbb 100644
>> --- a/gdb/arc-tdep.c
>> +++ b/gdb/arc-tdep.c
>> @@ -44,7 +44,6 @@
>>   
>>   /* Standard headers.  */
>>   #include <algorithm>
>> -#include <sstream>
>>   
>>   /* The frame unwind cache for ARC.  */
>>   
>> @@ -2100,16 +2099,16 @@ arc_check_tdesc_feature (struct tdesc_arch_data *tdesc_data,
>>   
>>         if (!found && reg.required_p)
>>   	{
>> -	  std::ostringstream reg_names;
>> +	  std::string reg_names;
>>   	  for (std::size_t i = 0; i < reg.names.size(); ++i)
>>   	    {
>>   	      if (i == 0)
>> -		reg_names << "'" << reg.names[0] << "'";
>> +		string_appendf (reg_names, "'%s'", reg.names[0]);
>>   	      else
>> -		reg_names << " or '" << reg.names[0] << "'";
>> +		string_appendf (reg_names, " or '%s'", reg.names[i]);
> 

Hi Simon,

thanks for the review.

> Looks like you fixed a bug here (0 -> i).

Yes, that's what I meant by "fix an array index bug".

Thanks,
- Tom

> Approved-By: Simon Marchi <simon.marchi@efficios.com>
> 
> Simon