utmp symbol conflict

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Hello,

The shellinabox project
(https://github.com/shellinabox/shellinabox) fails to build with musl
due to the following define in musl's utmp.h:

#define utmp utmpx

Indeed shellinabox/launcher.c has the following piece of code
(https://github.com/shellinabox/shellinabox/blob/master/shellinabox/launcher.c#L1572) :

    struct utmpx utmpx            = utmp->utmpx;
    if (service->useLogin || service->authUser) {
      utmpx.ut_type               = LOGIN_PROCESS;
      memset(utmpx.ut_host, 0, sizeof(utmpx.ut_host));
    }

Where "utmp" is of type "struct Utmp *", which is an internal structure
type defined as:

struct Utmp {
  const char   pid[32];
  int          pty;
  int          useLogin;
#ifdef HAVE_UTMPX_H
  struct utmpx utmpx;
#endif
};

Unfortunately, with musl's definition #define utmp utmpx, the line:

	struct utmpx utmpx            = utmp->utmpx;

gets turned after pre-processing to:

	struct utmpx utmpx            = utmpx->utmpx;

which obviously causes a build failure:

shellinabox/launcher.c: In function ‘childProcess’:
shellinabox/launcher.c:1576:41: error: invalid type argument of ‘->’ (have ‘struct utmpx’)
     struct utmpx utmpx            = utmp->utmpx;
                                         ^
I don't think the symbol "utmp" as a variable name is reserved, so is
the #define utmp utmpx done by musl really a legal thing to do?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com