Installation guide

• The DIGITAL UNIX C compiler does not allow you to modify a type you

create with the typedef statement. For example, the following

statement is invalid on DIGITAL UNIX systems:

typedef int account;

account monthly;

unsigned account display_account;

To achieve this effect on DIGITAL UNIX systems, you must create both

a signed and unsigned type, as shown:

typedef int account;

typedef unsigned int display_variable;

account monthly;

display_variable display_account;

• On DIGITAL UNIX systems, you cannot declare or deﬁne a type within

a function prototype. The ULTRIX compiler allows this, although doing

so causes the parameter to be incompatible with any other type.

For example, suppose the structure S shown in the following

declaration has not been declared previously. Any further type

matching of the parameter list results in an error. At the end of the

prototype, the scope ends, which means that S is no longer available:

int convert_array (struct S *p);

On DIGITAL UNIX systems, you must declare the structure S outside

of the function prototype, as shown:

struct S *p;

int convert_array(struct S);

• If you include a directory speciﬁcation as an option to the #line

directive, the DIGITAL UNIX C preprocessor uses the directory as the

local directory for all subsequent #include directives. The ULTRIX C

preprocessor did not process the #line directives in this manner. To

force the compiler to search locally instead of using the #line directive

information, use the −I option to the cc command and specify the local

directory (the period character), as follows:

cc −g −O0 −I. −c sample_module.c

Since various C code generators (for example, lex and yacc) insert a

#line directive into the generated C code, you might encounter this

error inadvertently.

7–24 Migrating Your ULTRIX Application to a DIGITAL UNIX System