TABLE D-1 K&R Sun C Incompatibilities with Sun ANSI/ISO C
| Topic |
Sun C (K&R) |
Sun ANSI/ISO C |
envp argument to main() |
Allows envp as third argument to main(). |
Allows this third argument; however, this usage is not strictly conforming to the ANSI/ISO C standard. |
|
Keywords |
Treats the identifiers const, volatile, and signed as ordinary identifiers. |
const, volatile, and signed are keywords. |
extern and static functions declarations inside a block |
Promotes these function declarations to file scope. |
The ANSI/ISO standard does not guarantee that block scope function declarations are promoted to file scope. |
|
Identifiers |
Allows dollar signs ($) in identifiers. |
$ not allowed. |
long float types |
Accepts long float declarations and treats these as double(s). |
Does not accept these declarations. |
|
Multi-character character-constants |
int mc = 'abcd';
yields:
abcd |
int mc = 'abcd';
yields:
dcba |
|
Integer constants |
Accepts 8 or 9 in octal escape sequences. |
Does not accept 8 or 9 in octal escape sequences. |
|
Assignment operators |
Treats the following operator pairs as two tokens, and as a consequence, permits white space between them:
*=, /=, %=, +=, -=, <<=, >>=, &=, ^=, |= |
Treats them as single tokens, and therefore disallows white space in between. |
|
Unsigned preserving semantics for expressions |
Supports unsigned preserving, that is, unsigned char/shorts are converted into unsigned int(s). |
Supports value-preserving, that is, unsigned char/short(s) are converted into int(s). |
|
Single/double precision calculations |
Promotes the operands of floating point expressions to double.
Functions which are declared to return floats always promote their return values to doubles. |
Allows operations on floats to be performed in single precision calculations.
Allows float return types for these functions. |
Name spaces of struct/union members |
Allows struct, union, and arithmetic types using member selection operators ('.', '->') to work on members of other struct(s) or unions. |
Requires that every unique struct/union have its own unique name space. |
A cast as an lvalue |
Supports casts as lvalue(s). For example:
(char *)ip = &char; |
Does not support this feature. |
Implied int declarations |
Supports declarations without an explicit type specifier. A declaration such as num; is treated as implied int. For example:
num; /*num implied as an int*/
int num2; /* num2 explicitly*/
/* declared an int */ |
The num; declaration (without the explicit type specifier int) is not supported, and generates a syntax error. |
|
Empty declarations |
Allows empty declarations, such as:
int; |
Except for tags, disallows empty declarations. |
|
Type specifiers on type definitions |
Allows type specifiers such as unsigned, short, long on typedefs declarations. For example:
typedef short small;
unsigned small x; |
Does not allow type specifiers to modify typedef declarations. |
|
Types allowed on bit fields |
Allows bit fields of all integral types, including unnamed bit fields.
The ABI requires support of unnamed bit fields and the other integral types. |
Supports bitfields only of the type int, unsigned int and signed int. Other types are undefined. |
|
Treatment of tags in incomplete declarations |
Ignores the incomplete type declaration. In the following example, f1 refers to the outer struct:
struct x { . . . } s1;
{struct x; struct y {struct x f1; } s2; struct x
{ . . . };} |
In an ANSI/ISO-conforming implementation, an incomplete struct or union type specifier hides an enclosing declaration with the same tag. |
Mismatch on struct/union/enum declarations |
Allows a mismatch on the struct/enum/union type of a tag in nested struct/union declarations. In the following example, the second declaration is treated as a struct:
struct x {.. . }s1; {union x s2;. . .} |
Treats the inner declaration as a new declaration, hiding the outer tag. |
|
Labels in expressions |
Treats labels as (void *) lvalues. |
Does not allow labels in expressions. |
switch condition type |
Allows float(s) and double(s) by converting them to int(s). |
Evaluates only integral types (int, char, and enumerated) for the switch condition type. |
|
Syntax of conditional inclusion directives |
The preprocessor ignores trailing tokens after an #else or #endif directive. |
Disallows such constructs. |
Token-pasting and the ## preprocessor operator |
Does not recognize the ## operator. Token-pasting is accomplished by placing a comment between the two tokens being pasted:
#define PASTE(A,B) A/*any comment*/B |
Defines ## as the preprocessor operator that performs token-pasting, as shown in this example:
#define PASTE(A,B) A##B
Furthermore, the Sun ANSI/ISO C preprocessor doesn't recognize the Sun C method. Instead, it treats the comment between the two tokens as white space. |
|
Preprocessor rescanning |
The preprocessor recursively substitutes:
#define F(X) X(arg)
F(F)
yields
arg(arg) |
A macro is not replaced if it is found in the replacement list during the rescan:
#define F(X)X(arg)
F(F)
yields:
F(arg) |
typedef names in formal parameter lists |
You can use typedef names as formal parameter names in a function declaration. "Hides" the typedef declaration. |
Disallows the use of an identifier declared as a typedef name as a formal parameter. |
|
Implementation-specific initializations of aggregates |
Uses a bottom-up algorithm when parsing and processing partially elided initializers within braces:
struct{ int a[3]; int b; }\w[]={{1},2};
yields
sizeof(w)=16
w[0].a=1,0,0
w[0].b=2 |
Uses a top-down parsing algorithm. For example:
struct{int a[3];int b;}\
w[]={{1},2};
yields
sizeof(w)=32
w[0].a=1,0,0
w[0].b=0
w[1].a=2,0,0
w[1].b=0 |
Comments spanning include files |
Allows comments which start in an #include file to be terminated by the file that includes the first file. |
Comments are replaced by a white-space character in the translation phase of the compilation, which occurs before the #include directive is processed. |
|
Formal parameter substitution within a character constant |
Substitutes characters within a character constant when it matches the replacement list macro:
#define charize(c)'c'
charize(Z)
yields:
'Z' |
The character is not replaced:
#define charize(c) 'c'
charize(Z)
yields:
'c' |
|
Formal parameter substitution within a string constant |
The preprocessor substitutes a formal parameter when enclosed within a string constant:
#define stringize(str) 'str'
stringize(foo)
yields:
"foo" |
The # preprocessor operator should be used:
#define stringize(str) 'str'
stringize(foo)
yields:
"str"
|
|
Preprocessor built into the compiler "front-end" |
Compiler calls cpp(1).
Components used in the compiling are:
cpp
ccom
iropt
cg
inline
as
ld
Note: iropt and cg are invoked only with the following options:
-O -xO2 -xO3 -xO4 -xa -fast
inline is invoked only if an inline template file (file.il) is provided. |
Preprocessor (cpp) is built directly into acomp, so cpp is not directly involved, except in -Xs mode.
Components used in the compiling are:
cpp (-Xs mode only)
acomp
iropt
cg
ld
Note: iropt and cg are invoked only with the following options:
-O -xO2 -xO3 -xO4 -xa -fast |
|
Line concatenation with backslash |
Does not recognize the backslash character in this context. |
Requires that a newline character immediately preceded by a backslash character be spliced together. |
|
Trigraphs in string literals |
Does not support this ANSI/ISO C feature. |
|
asm keyword |
asm is a keyword. |
asm is treated as an ordinary identifier. |
|
Linkage of identifiers |
Does not treat uninitialized static declarations as tentative declarations. As a consequence, the second declaration will generate a 'redeclaration' error, as in:
static int i = 1;
static int i;
|
Treats uninitialized static declarations as tentative declarations. |
|
Name spaces |
Distinguishes only three : struct/union/enum tags, members of struct/union/enum, and everything else. |
Recognizes four distinct name spaces: label names, tags (the names that follow the keywords struct, union or enum), members of struct/union/enum, and ordinary identifiers. |
long double type |
Not supported. |
Allows long double type declaration. |
|
Floating point constants |
The floating point suffixes, f, l, F, and L, are not supported. |
|
|
Unsuffixed integer constants can have different types |
The integer constant suffixes u and U are not supported. |
|
|
Wide character constants |
Does not accept the ANSI/ISO C syntax for wide character constants, as in:
wchar_t wc = L'x'; |
Supports this syntax. |
'\a' and '\x' |
Treats them as the characters 'a' and 'x'. |
Treats '\a' and '\x' as special escape sequences. |
|
Concatenation of string literals |
Does not support the ANSI/ISO C concatenation of adjacent string literals. |
|
|
Wide character string literal syntax |
Does not support the ANSI/ISO C wide character, string literal syntax shown in this example:
wchar_t *ws = L"hello"; |
Supports this syntax. |
Pointers:
void * versus char * |
Supports the ANSI/ISO C void * feature. |
|
|
Unary plus operator |
Does not support this ANSI/ISO C feature. |
|
|
Function prototypes-- ellipses |
Not supported. |
ANSI/ISO C defines the use of ellipses "..." to denote a variable argument parameter list. |
|
Type definitions |
Disallows typedefs to be redeclared in an inner block by another declaration with the same type name. |
Allows typedefs to be redeclared in an inner block by another declaration with the same type name. |
Initialization of extern variables |
Does not support the initialization of variables explicitly declared as extern. |
Treats the initialization of variables explicitly declared as extern, as definitions. |
|
Initialization of aggregates |
Does not support the ANSI/ISO C initialization of unions or automatic structures. |
|
|
Prototypes |
Does not support this ANSI/ISO C feature. |
|
|
Syntax of preprocessing directive |
Recognizes only those directives with a # in the first column. |
ANSI/ISO C allows leading white-space characters before a # directive. |
The # preprocessor operator |
Does not support the ANSI/ISO C # preprocessor operator. |
|
#error directive |
Does not support this ANSI/ISO C feature. |
|
|
Preprocessor directives |
Supports two pragmas, unknown_control_flow and makes_regs_inconsistent along with the #ident directive. The preprocessor issues warnings when it finds unrecognized pragmas. |
Does not specify its behavior for unrecognized pragmas. |
|
Predefined macro names |
These ANSI/ISO C-defined macro names are not defined:
__STDC__ __DATE__
__TIME__ __LINE__ |
|
