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Date: Thu, 4 Aug 2016 22:28:52 +0200
From: Thomas Petazzoni <>
Subject: utmp symbol conflict


The shellinabox project
( 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
( :

    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;
  struct utmpx utmpx;

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 Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering

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