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[Notes]
C Compiler Package for RH850 Family
Outline
When using the C compiler package for RH850 family CC-RH, note the following points.
1. Point for caution regarding constant expressions that include type conversion from the floating-point type to
the 64-bit integer type (No.23)
2. Point for caution when the -Xmisra2012 option is specified (No.24)
Note: The number following the note is an identifying number for the precautionary note.
1. Point for caution regarding constant expressions that include type conversion from
the floating-point type to the 64-bit integer type (No.23)
1.1 Applicable Products
CC-RH V1.02.00 to V2.00.00
1.2 Details
The result of a constant expression that includes type conversion from the floating-point type to the 64-bit integer type
may be incorrect.
1.3 Conditions
An error occurs when all of the following conditions (1) through (5) are met.
(1) The -Xround=zero option is specified.
(2) A constant expression is written.
(3) A subexpression in (2)
(Note1)
includes a constant expression of the float, double, or long double floating-point type.
Note 1: Cases where (2) itself is a constant expression of the float, double, or long double type are included.
(4) There is a type conversion from the subexpression in (3) to the signed long long or unsigned long long 64-bit integer
type, including implicit type conversion.
(5) The value of the subexpression in (3) falls within the following range:
(5-1) When converting a float-type constant expression or a double- or long double-type constant expression
with the -Xdbl_size=4 option specified to the following type:
(5-1-a) When converting to the signed long long type:
・ 2.147483e+09 to 3.602880e+16
or
・ -2.147483e+09 to -3.602880e+16
(5-1-b) When converting to the unsigned long long type:
・ 4.294967e+09 to 3.602880e+16
(5-2) When converting a double-type constant expression with the -Xdbl_size=8 option specified or a long double-
type constant expression to the following type:
(5-2-a) When converting to the signed long long type:
・ 2.147483e+09 or more
or
-2.147483e+09 or less
(5-2-b) When converting to the unsigned long long type:
・ 4.294967e+09 or more
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1.4 Example
The example of an error is shown below.
long long ll = (long long)(123456789123.0+123+456); // Condition (2)(3)(4)(5)
-Condition (2) is met because a constant expression “(long long)(123456789123.0+123+456)” is written.
-Condition (3) is met because a subexpression of the constant expression includes the double type (123456789123.0).
-Condition (4) is met because conversion to the long long type is included.
-Condition (5-2-a) is met because the calculation result (123456789702.0) of the constant expression falls within the
range.
[Assembler source code (wrong compilation result)]
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_ll:
. ddw 0xFFFFFFFFBE991CC6
-Line 2: Compilation result applicable to this note is produced when condition (1) and condition (2) through (5) in the
example above are met.
[Assembler source code (correct compilation result)]
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_ll:
. ddw 0x0000001CBE991CC6
-Line2: The correct result of compilation is shown above.
1.5 Workaround
To avoid this problem, take either of the following steps.
(1) Describe the constant expression in (2) as a converted integer-type constant. Refer to [Workaround example of C
source code (1)] below.
(2) Describe conversion as code-based runtime processing using either (2-1) or (2-2) below instead of a constant
expression.
(2-1) Assign the value to the 64-bit integer type variable via double-type variable. Refer to [Workaround example
of C source code (2-1)] below.
(2-2) Replace the variable with an inline function call that returns a double type value. Refer to [Workaround
example of C source code (2-2)] below.
[Workaround example of C source code (1)]
long long ll = 123456789702ll;
[Workaround example of C source code (2-1)]
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[Workaround example of C source code (2-2)]
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#pragma inline dvalue
static double dvalue(){
return 123456789123.0+123+456; //Define the inline function returning double
//type value
}
void func(){
long long ll = dvalue(); //Call the inline function and assign it to the
//variable II
}
1.6 Schedule for Fixing the Problem
This problem is fixed in CC-RH V2.01.00 and V1.07.01. (Scheduled to be released on January 21.)
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2. Point for caution when the -Xmisra2012 option is specified. (No.24)
2.1 Applicable Products
CC-RH V1.04.00 to V2.00.00 [Professional edition] (Rule 16.1 and 16.4)
CC-RH V1.07.00 to V2.00.00 [Professional edition] (Rule 15.6, 15.7, 16.1, and 16.2)
2.2 Details
When checking source code against MISRA-C:2012 rules by specifying -Xmisra2012 option, the compiler may
output a message for a code which does not violate the rules and may not output a message for a code which violates
the rules.
MISRA-C is a set of software development guidelines whose purpose is to maintain the safety, portability and
reliability of embedded systems programmed in the C language.
2.3 Conditions
An error occurs when the following rule numbers are specified to be checked.
⚫ Rule 15.6
No message is output for a code that violates the rule if the -lang=c99 option is specified.
⚫ Rule 15.7
No message is output for a code that violates the rule if the -lang=c99 option is specified.
⚫ Rule 16.1
No message is output for a code that violates the rule if all of the following conditions are met:
(1) “{“ is written immediately after a switch statement (controlling expression).
(2) Both a case clause and a default clause are written in the switch statement (1).
(3) Each case clause and default clause in (2) ends with a break statement or a compound statement
(Note1)
(block) which includes a break statement at the end.
(4) At least one of the case clauses or default clauses in (3) meets all the conditions below.
(4-1) A compound statement (block) which is neither a selection statement (if or switch) nor a repeat
statement (while, do-while, or for) is written at the end.
(4-2) A statement is written before the compound statement (block) in (4-1).
Note 1: A compound statement is a statement enclosed with “{ }”. An if statement enclosed with “{ }”
is also a compound statement.
⚫ Rule 16.2
No message is output for a code that violates the rule if all of the following conditions are met.
(1) The -lang=c99 option is specified.
(2) A case or default label is written immediately after switch (controlling expression) without “{”.
⚫ Rule 16.4
A message may be output for a code that does not violate the rule if either of the following conditions is met:
(1) -lang=c is specified and a compound statement (block) is written in the function definition.
(2) -lang=c99 is specified, and a compound statement (block), selection statement (if or switch), or repeat
statement (while, do-while, or for) is written in the function definition.
This includes a case where a selection statement or repeat statement is written without “{ }”.
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2.4 Example
The example of an error is shown below. Characters in red are the parts corresponding to the conditions.
[C source code] (rule 16.1)
Although the C source code above violates rule 16.1 of MISRA C: 2012, no message is output.
Lines 3 and 12: Condition (1) is met because “{” is written immediately after switch (controlling expression).
Lines 4 and 10: Condition (2) is met because both a case clause and a default clause are written.
Lines 8 and 11: Condition (3) is met because the case clause and default clause end with a break statement.
Lines 6 and 9: Condition (4-1) is met because the case clause ends with a compound statement (block).
Line 5: Condition (4-2) is met because a statement is written before a compound statement (block).
[C source code] (for rule 16.2)
The C source code above violates rule 16.2 of MISRA C:2012. Although a message is output when -lang=c is specified,
no message is output when -lang=c99 is specified.
Lines 3 and 4: Condition (2) is met because a case label is written without “{” immediately after switch (controlling
expression).
2.5 Workaround
There is no workaround for this problem.
2.6 Schedule for Fixing the Problem
This problem is fixed in CC-RH V2.01.00 and V1.07.01. (Scheduled to be released on January 21.)
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int x;
void func(void) {
switch(x) { // Condition (1)
case 1: // Condition (2)
++x; // Condition (4-2)
{ // Condition (4-1)
--x;
break; // Condition (3)
} // Condition (4-1)
default: // Condition (2)
break; // Condition (3)
} // Condition (1)
}
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int x;
void func(void) {
switch(x) // Condition (2)
case 1: // Condition (2)
break;
}
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Revision History
Rev.
Date
Description
Page
Summary
1.00
Jan. 16, 2019
-
First edition issued
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