CODEWITHSUNDEEP
clinuxredhat
Bernardo Wilberger
Bernardo Wilberger

Reputation: 85

Can't compile when including ucontext.h

Using gcc, I get these errors when compiling something that makes use of ucontext.h

    /usr/include/sys/ucontext.h: At top level:
    /usr/include/sys/ucontext.h:138: error: expected identifier or ‘(’ before numeric constant
    /usr/include/sys/ucontext.h:139: error: expected ‘;’ before ‘stack_t’

Looking at ucontext.h, this is what seems to cause:

    134 /* Userlevel context.  */
    135 typedef struct ucontext
    136   {
    137     unsigned long int uc_flags;
    138     struct ucontext *uc_link;
    139     stack_t uc_stack;
    140     mcontext_t uc_mcontext;
    141     __sigset_t uc_sigmask;
    142     struct _libc_fpstate __fpregs_mem;
    143   } ucontext_t;

How could line 138 and 139 raise these errors? Don't know what to do since this is a standard sys header.

Upvotes: 2

Views: 2130

Answers (1)

Michael Kruglos
Michael Kruglos

Reputation: 1286

This problem is probably caused by #define somewhere in the code, which defines uc_link as some integer.

Example:

#define uc_link 22

The most efficient way to find it in Unix/Linux would be to run grep -r "uc_link" . on your source code directory. If you use git to manage your source code you can do git grep "uc_link" instead.

If this define is present in one file and you use ucontext.h in it, then you should try to decouple your ucontext logic from the logic which demands this #define.

Also, I must note that it is a bad practice to have #defines which are not ALL_CAPS. One of the reasons is well represented by the problem you encountered, another reason is the fact that everyone expects them to be ALL_CAPS and your code becomes less intelligible and less readable to other programmers who may want to collaborate with you.

Upvotes: 3

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