ARMCC: Internal Fault 0xda55d9

Information in this knowledgebase article applies to:

• Keil MDK
• Arm Compiler 5.04u1 or later versions of Arm Compiler 5

SYMPTOM

Project is built with options --c99 -Otime and -O2 or -O3. On a specific source file, the compiler shows the following message in the build output:

Internal fault: [0xda55d9:50#####] in {function_name}
Please contact your supplier.

CAUSE

In this file, the function from fault message is within the scope of a named register variable and causes the compiler to fault. Arm Compiler 5 does not commit to a successful compile with every use-case of named register variables. See the Restrictions section in the description of named register variables.

Here is one code example that can cause the issue. With the compiler command-line options above, use

struct b
{
   int w;
};

register int a  __asm( "r0" );

struct b B;

void func1() {
  char * q;
  char * c[] = {
          [0] = "A",
          [1] = "B",
          [2] = "C",
          [3] = "D",
          [4] = "E",
          [5] = "F",
          [6] = "G",
          [7] = "H",
          [8] = "I",
          [9] = "J",
          [10] = "K",
          [11] = "L",     //comment out this line and compile is successful

  };

  while (1) {
     if( c[ B.w ] )
        q = "A";
     }

}

For this example, a structure or a union can be used as "b". The named register line can also be located in an included header file because this is in the same scope. The function must use a continuous loop, and the array "c" must use designated initializers.

RESOLUTION

The workaround is to wrap the function definition in:

#pragma push
#pragma O1 //or #pragma Ospace
//func1() definition
#pragma pop

Another workaround is to limit the scope of named register variables to source files that do not use similar code to the example above.

STATUS

This issue will not be resolved in Arm Compiler 5. The current development effort is focused on ARM Compiler 6. Critical issues in Arm Compiler 5 will be resolved and some safety-critical versions will still be maintained, but major new features, like including new ways to handle named register variables, will not be added to Arm Compiler 5.

MORE INFORMATION

• Refer to Compiler support for accessing registers using named register variables to learn more about use-cases for this feature, including examples.
• Refer to Named register variables to learn more about syntax, usage, and restrictions of this feature, including examples.

Last Reviewed: Monday, January 11, 2021