diff --git a/cachegrind/cg_main.c b/cachegrind/cg_main.c
index 4f0bef4..73d05a4 100644
--- a/cachegrind/cg_main.c
+++ b/cachegrind/cg_main.c
@@ -807,6 +807,7 @@
 static void fprint_CC_table_and_calc_totals(void)
 {
    Int     fd;
+   SysRes  sres;
    Char    buf[512];
    fileCC *curr_fileCC;
    fnCC   *curr_fnCC;
@@ -815,9 +816,9 @@
 
    VGP_PUSHCC(VgpCacheResults);
 
-   fd = VG_(open)(cachegrind_out_file, VKI_O_CREAT|VKI_O_TRUNC|VKI_O_WRONLY,
-                                       VKI_S_IRUSR|VKI_S_IWUSR);
-   if (fd < 0) {
+   sres = VG_(open)(cachegrind_out_file, VKI_O_CREAT|VKI_O_TRUNC|VKI_O_WRONLY,
+                                         VKI_S_IRUSR|VKI_S_IWUSR);
+   if (sres.isError) {
       // If the file can't be opened for whatever reason (conflict
       // between multiple cachegrinded processes?), give up now.
       VG_(message)(Vg_UserMsg,
@@ -826,6 +827,8 @@
       VG_(message)(Vg_UserMsg,
          "       ... so simulation results will be missing.");
       return;
+   } else {
+      fd = sres.val;
    }
 
    // "desc:" lines (giving I1/D1/L2 cache configuration).  The spaces after
diff --git a/coregrind/m_aspacemgr/read_procselfmaps.c b/coregrind/m_aspacemgr/read_procselfmaps.c
index febef75..67373c8 100644
--- a/coregrind/m_aspacemgr/read_procselfmaps.c
+++ b/coregrind/m_aspacemgr/read_procselfmaps.c
@@ -98,21 +98,22 @@
 
 static void read_procselfmaps ( void )
 {
-   Int n_chunk, fd;
+   Int    n_chunk;
+   SysRes fd;
    
    /* Read the initial memory mapping from the /proc filesystem. */
    fd = VG_(open) ( "/proc/self/maps", VKI_O_RDONLY, 0 );
-   if (fd < 0) {
+   if (fd.isError) {
       VG_(message)(Vg_UserMsg, "FATAL: can't open /proc/self/maps");
       VG_(exit)(1);
    }
    buf_n_tot = 0;
    do {
-      n_chunk = VG_(read) ( fd, &procmap_buf[buf_n_tot],
+      n_chunk = VG_(read) ( fd.val, &procmap_buf[buf_n_tot],
                             M_PROCMAP_BUF - buf_n_tot );
       buf_n_tot += n_chunk;
    } while ( n_chunk > 0 && buf_n_tot < M_PROCMAP_BUF );
-   VG_(close)(fd);
+   VG_(close)(fd.val);
    if (buf_n_tot >= M_PROCMAP_BUF-5) {
       VG_(message)(Vg_UserMsg, "FATAL: M_PROCMAP_BUF is too small; "
                                "increase it and recompile");
diff --git a/coregrind/m_debuginfo/symtab.c b/coregrind/m_debuginfo/symtab.c
index 0af108f..8f1286d 100644
--- a/coregrind/m_debuginfo/symtab.c
+++ b/coregrind/m_debuginfo/symtab.c
@@ -1145,16 +1145,17 @@
 static
 Addr open_debug_file( Char* name, UInt crc, UInt* size )
 {
-   Int fd;
+   SysRes fd;
    struct vki_stat stat_buf;
    Addr addr;
    UInt calccrc;
 
-   if ((fd = VG_(open)(name, VKI_O_RDONLY, 0)) < 0)
+   fd = VG_(open)(name, VKI_O_RDONLY, 0);
+   if (fd.isError)
       return 0;
 
-   if (VG_(fstat)(fd, &stat_buf) != 0) {
-      VG_(close)(fd);
+   if (VG_(fstat)(fd.val, &stat_buf) != 0) {
+      VG_(close)(fd.val);
       return 0;
    }
 
@@ -1165,13 +1166,13 @@
    
    if ((addr = (Addr)VG_(mmap)(NULL, *size, VKI_PROT_READ,
                                VKI_MAP_PRIVATE|VKI_MAP_NOSYMS, 
-                               0, fd, 0)) == (Addr)-1) 
+                               0, fd.val, 0)) == (Addr)-1) 
    {
-      VG_(close)(fd);
+      VG_(close)(fd.val);
       return 0;
    }
 
-   VG_(close)(fd);
+   VG_(close)(fd.val);
    
    calccrc = calc_gnu_debuglink_crc32(0, (UChar*)addr, *size);
    if (calccrc != crc) {
@@ -1226,7 +1227,7 @@
    ElfXX_Ehdr*   ehdr;       /* The ELF header                          */
    ElfXX_Shdr*   shdr;       /* The section table                       */
    UChar*        sh_strtab;  /* The section table's string table        */
-   Int           fd;
+   SysRes        fd;
    Int           i;
    Bool          ok;
    Addr          oimage;
@@ -1251,16 +1252,16 @@
    n_oimage = stat_buf.st_size;
 
    fd = VG_(open)(si->filename, VKI_O_RDONLY, 0);
-   if (fd < 0) {
+   if (fd.isError) {
       ML_(symerr)("Can't open .so/.exe to read symbols?!");
       return False;
    }
 
    oimage = (Addr)VG_(mmap)( NULL, n_oimage, 
                              VKI_PROT_READ, VKI_MAP_PRIVATE|VKI_MAP_NOSYMS, 
-                             0, fd, 0 );
+                             0, fd.val, 0 );
 
-   VG_(close)(fd);
+   VG_(close)(fd.val);
 
    if (oimage == ((Addr)(-1))) {
       VG_(message)(Vg_UserMsg, "warning: mmap failed on %s", si->filename );
diff --git a/coregrind/m_errormgr.c b/coregrind/m_errormgr.c
index 11e7acb..50e1ab2 100644
--- a/coregrind/m_errormgr.c
+++ b/coregrind/m_errormgr.c
@@ -895,22 +895,25 @@
 static void load_one_suppressions_file ( Char* filename )
 {
 #  define N_BUF 200
-   Int   fd, i;
-   Bool  eof;
-   Char  buf[N_BUF+1];
-   Char* tool_names;
-   Char* supp_name;
-   Char* err_str = NULL;
+   SysRes sres;
+   Int    fd, i;
+   Bool   eof;
+   Char   buf[N_BUF+1];
+   Char*  tool_names;
+   Char*  supp_name;
+   Char*  err_str = NULL;
    SuppLoc tmp_callers[VG_MAX_SUPP_CALLERS];
 
-   fd = VG_(open)( filename, VKI_O_RDONLY, 0 );
-   if (fd < 0) {
+   fd   = -1;
+   sres = VG_(open)( filename, VKI_O_RDONLY, 0 );
+   if (sres.isError) {
       VG_(message)(Vg_UserMsg, "FATAL: can't open suppressions file '%s'", 
                    filename );
       VG_(exit)(1);
    }
+   fd = sres.val;
 
-#define BOMB(S)  { err_str = S;  goto syntax_error; }
+#  define BOMB(S)  { err_str = S;  goto syntax_error; }
 
    while (True) {
       /* Assign and initialise the two suppression halves (core and tool) */
diff --git a/coregrind/m_libcfile.c b/coregrind/m_libcfile.c
index 8d3865f..16c8087 100644
--- a/coregrind/m_libcfile.c
+++ b/coregrind/m_libcfile.c
@@ -84,11 +84,10 @@
       return False;
 }
 
-/* Returns -1 on failure. */
-Int VG_(open) ( const Char* pathname, Int flags, Int mode )
+SysRes VG_(open) ( const Char* pathname, Int flags, Int mode )
 {  
    SysRes res = VG_(do_syscall3)(__NR_open, (UWord)pathname, flags, mode);
-   return res.isError ? -1 : res.val;
+   return res;
 }
 
 void VG_(close) ( Int fd )
diff --git a/coregrind/m_main.c b/coregrind/m_main.c
index e33cdad..6f4fee9 100644
--- a/coregrind/m_main.c
+++ b/coregrind/m_main.c
@@ -297,22 +297,23 @@
 static char* get_file_clo(char* dir)
 {
 #  define FLEN 512
-   Int fd, n;
+   Int    n;
+   SysRes fd;
    struct vki_stat s1;
-   char* f_clo = NULL;
-   char filename[FLEN];
+   Char* f_clo = NULL;
+   Char  filename[FLEN];
 
    snprintf(filename, FLEN, "%s/.valgrindrc", ( NULL == dir ? "" : dir ) );
    fd = VG_(open)(filename, 0, VKI_S_IRUSR);
-   if ( fd > 0 ) {
-      if ( 0 == VG_(fstat)(fd, &s1) ) {
+   if ( !fd.isError ) {
+      if ( 0 == VG_(fstat)(fd.val, &s1) ) {
          f_clo = malloc(s1.st_size+1);
          vg_assert(f_clo);
-         n = VG_(read)(fd, f_clo, s1.st_size);
+         n = VG_(read)(fd.val, f_clo, s1.st_size);
          if (n == -1) n = 0;
          f_clo[n] = '\0';
       }
-      VG_(close)(fd);
+      VG_(close)(fd.val);
    }
    return f_clo;
 #  undef FLEN
@@ -1160,7 +1161,9 @@
       VG_(memset)(info, 0, sizeof(*info));
    } else {
       Int ret;
-      VG_(clexecfd) = VG_(open)(exec, VKI_O_RDONLY, VKI_S_IRUSR);
+      /* HACK: assumes VG_(open) always succeeds */
+      VG_(clexecfd) = VG_(open)(exec, VKI_O_RDONLY, VKI_S_IRUSR)
+                      .val;
       ret = VG_(do_exec)(exec, info);
       if (ret != 0) {
          fprintf(stderr, "valgrind: do_exec(%s) failed: %s\n",
@@ -1407,8 +1410,9 @@
 
 static void process_cmd_line_options( UInt* client_auxv, const char* toolname )
 {
-   Int  i, eventually_log_fd;
-   Int  toolname_len = VG_(strlen)(toolname);
+   SysRes sres;
+   Int    i, eventually_log_fd;
+   Int    toolname_len = VG_(strlen)(toolname);
    enum {
       VgLogTo_Fd,
       VgLogTo_File,
@@ -1724,30 +1728,40 @@
 	 }
 
 	 for (;;) {
-	    if (seq == 0)
-	       VG_(sprintf)( logfilename, "%s%s%s.pid%d",
-                             VG_(clo_log_name), 
-                             qual ? "." : "", qual ? qual : "",
-                             pid );
-	    else
-	       VG_(sprintf)( logfilename, "%s%s%s.pid%d.%d",
-			     VG_(clo_log_name), 
-                             qual ? "." : "", qual ? qual : "",
-                             pid, seq );
+            HChar pidtxt[20], seqtxt[20];
+
+            VG_(sprintf)(pidtxt, "%d", pid);
+
+            if (seq == 0)
+               seqtxt[0] = 0;
+            else
+               VG_(sprintf)(seqtxt, ".%d", seq);
+
 	    seq++;
 
+            /* Result:
+                  if (qual)      base_name ++ "." ++ qual ++ seqtxt
+                  if (not qual)  base_name ++ "." ++ pid  ++ seqtxt
+            */
+            VG_(sprintf)( logfilename, 
+                          "%s.%s%s",
+                          VG_(clo_log_name), 
+                          qual ? qual : pidtxt,
+                          seqtxt );
+
             // EXCL: it will fail with EEXIST if the file already exists.
-	    eventually_log_fd 
+            sres
 	       = VG_(open)(logfilename, 
 			   VKI_O_CREAT|VKI_O_WRONLY|VKI_O_EXCL|VKI_O_TRUNC, 
 			   VKI_S_IRUSR|VKI_S_IWUSR);
-	    if (eventually_log_fd >= 0) {
+	    if (!sres.isError) {
+               eventually_log_fd = sres.val;
 	       VG_(clo_log_fd) = VG_(safe_fd)(eventually_log_fd);
 	       break; /* for (;;) */
 	    } else {
                // If the file already existed, we try the next name.  If it
                // was some other file error, we give up.
-	       if (eventually_log_fd != -VKI_EEXIST) {
+	       if (sres.val != VKI_EEXIST) {
 		  VG_(message)(Vg_UserMsg, 
 			       "Can't create/open log file '%s.pid%d'; giving up!", 
 			       VG_(clo_log_name), pid);
@@ -1764,11 +1778,12 @@
          vg_assert(VG_(clo_log_name) != NULL);
          vg_assert(VG_(strlen)(VG_(clo_log_name)) <= 900); /* paranoia */
 
-         eventually_log_fd 
+         sres
             = VG_(open)(VG_(clo_log_name),
                         VKI_O_CREAT|VKI_O_WRONLY|VKI_O_TRUNC, 
                         VKI_S_IRUSR|VKI_S_IWUSR);
-         if (eventually_log_fd >= 0) {
+         if (!sres.isError) {
+            eventually_log_fd = sres.val;
             VG_(clo_log_fd) = VG_(safe_fd)(eventually_log_fd);
          } else {
             VG_(message)(Vg_UserMsg, 
@@ -1937,7 +1952,7 @@
    }
 
    if (VG_(clo_verbosity) > 1) {
-      Int fd;
+      SysRes fd;
       if (log_to != VgLogTo_Fd)
          VG_(message)(Vg_DebugMsg, "");
       VG_(message)(Vg_DebugMsg, "Valgrind library directory: %s", VG_(libdir));
@@ -1952,12 +1967,12 @@
 
       VG_(message)(Vg_DebugMsg, "Contents of /proc/version:");
       fd = VG_(open) ( "/proc/version", VKI_O_RDONLY, 0 );
-      if (fd < 0) {
+      if (fd.isError) {
          VG_(message)(Vg_DebugMsg, "  can't open /proc/version");
       } else {
 #        define BUF_LEN    256
          Char version_buf[BUF_LEN];
-         Int n = VG_(read) ( fd, version_buf, BUF_LEN );
+         Int n = VG_(read) ( fd.val, version_buf, BUF_LEN );
          vg_assert(n <= BUF_LEN);
          if (n > 0) {
             version_buf[n-1] = '\0';
@@ -1965,7 +1980,7 @@
          } else {
             VG_(message)(Vg_DebugMsg, "  (empty?)");
          }
-         VG_(close)(fd);
+         VG_(close)(fd.val);
 #        undef BUF_LEN
       }
    }
diff --git a/coregrind/m_syswrap/syswrap-generic.c b/coregrind/m_syswrap/syswrap-generic.c
index a7fb692..f594a19 100644
--- a/coregrind/m_syswrap/syswrap-generic.c
+++ b/coregrind/m_syswrap/syswrap-generic.c
@@ -547,32 +547,33 @@
 
 void VG_(init_preopened_fds)()
 {
-   int f, ret;
+   int ret;
    struct vki_dirent d;
+   SysRes f;
 
    f = VG_(open)("/proc/self/fd", VKI_O_RDONLY, 0);
-   if(f == -1) {
+   if (f.isError) {
       do_hacky_preopened();
       return;
    }
 
-   while((ret = VG_(getdents)(f, &d, sizeof(d))) != 0) {
+   while ((ret = VG_(getdents)(f.val, &d, sizeof(d))) != 0) {
       if (ret == -1)
          goto out;
 
       if (VG_(strcmp)(d.d_name, ".") && VG_(strcmp)(d.d_name, "..")) {
          int fno = VG_(atoll)(d.d_name);
 
-         if (fno != f)
+         if (fno != f.val)
             if (VG_(clo_track_fds))
                record_fd_open_named(-1, fno);
       }
 
-      VG_(lseek)(f, d.d_off, VKI_SEEK_SET);
+      VG_(lseek)(f.val, d.d_off, VKI_SEEK_SET);
    }
 
-out:
-   VG_(close)(f);
+  out:
+   VG_(close)(f.val);
 }
 
 static
diff --git a/include/pub_tool_libcfile.h b/include/pub_tool_libcfile.h
index 2f80ec9..aad9fa0 100644
--- a/include/pub_tool_libcfile.h
+++ b/include/pub_tool_libcfile.h
@@ -35,18 +35,18 @@
    File-related functions.
    ------------------------------------------------------------------ */
 
-extern Int  VG_(open)   ( const Char* pathname, Int flags, Int mode );
-extern void VG_(close)  ( Int fd );
-extern Int  VG_(read)   ( Int fd, void* buf, Int count);
-extern Int  VG_(write)  ( Int fd, const void* buf, Int count);
-extern Int  VG_(pipe)   ( Int fd[2] );
-extern OffT VG_(lseek)  ( Int fd, OffT offset, Int whence);
+extern SysRes VG_(open)   ( const Char* pathname, Int flags, Int mode );
+extern void   VG_(close)  ( Int fd );
+extern Int    VG_(read)   ( Int fd, void* buf, Int count);
+extern Int    VG_(write)  ( Int fd, const void* buf, Int count);
+extern Int    VG_(pipe)   ( Int fd[2] );
+extern OffT   VG_(lseek)  ( Int fd, OffT offset, Int whence);
 
-extern Int  VG_(stat)   ( Char* file_name, struct vki_stat* buf );
-extern Int  VG_(fstat)  ( Int   fd,        struct vki_stat* buf );
-extern Int  VG_(dup2)   ( Int oldfd, Int newfd );
-extern Int  VG_(rename) ( Char* old_name, Char* new_name );
-extern Int  VG_(unlink) ( Char* file_name );
+extern Int    VG_(stat)   ( Char* file_name, struct vki_stat* buf );
+extern Int    VG_(fstat)  ( Int   fd,        struct vki_stat* buf );
+extern Int    VG_(dup2)   ( Int oldfd, Int newfd );
+extern Int    VG_(rename) ( Char* old_name, Char* new_name );
+extern Int    VG_(unlink) ( Char* file_name );
 
 // Returns False on failure (eg. if the buffer isn't big enough).
 extern Bool VG_(getcwd) ( Char* buf, SizeT size );
diff --git a/massif/ms_main.c b/massif/ms_main.c
index f436d0f..95d1566 100644
--- a/massif/ms_main.c
+++ b/massif/ms_main.c
@@ -1345,12 +1345,13 @@
  */
 static void write_hp_file(void)
 {
-   Int   i, j;
-   Int   fd, res;
-   Char *hp_file, *ps_file, *aux_file;
-   Char* cmdfmt;
-   Char* cmdbuf;
-   Int   cmdlen;
+   Int    i, j;
+   Int    fd, res;
+   SysRes sres;
+   Char  *hp_file, *ps_file, *aux_file;
+   Char*  cmdfmt;
+   Char*  cmdbuf;
+   Int    cmdlen;
 
    VGP_PUSHCC(VgpPrintHp);
    
@@ -1358,12 +1359,14 @@
    hp_file  = make_filename( base_dir, ".hp" );
    ps_file  = make_filename( base_dir, ".ps" );
    aux_file = make_filename( base_dir, ".aux" );
-   fd = VG_(open)(hp_file, VKI_O_CREAT|VKI_O_TRUNC|VKI_O_WRONLY,
-                           VKI_S_IRUSR|VKI_S_IWUSR);
-   if (fd < 0) {
+   sres = VG_(open)(hp_file, VKI_O_CREAT|VKI_O_TRUNC|VKI_O_WRONLY,
+                             VKI_S_IRUSR|VKI_S_IWUSR);
+   if (sres.isError) {
       file_err( hp_file );
       VGP_POPCC(VgpPrintHp);
       return;
+   } else {
+      fd = sres.val;
    }
 
    // File header, including command line
@@ -1658,9 +1661,10 @@
 static void
 write_text_file(ULong total_ST, ULong heap_ST)
 {
-   Int   fd, i;
-   Char* text_file;
-   Char* maybe_p = ( XHTML == clo_format ? "<p>" : "" );
+   SysRes sres;
+   Int    fd, i;
+   Char*  text_file;
+   Char*  maybe_p = ( XHTML == clo_format ? "<p>" : "" );
 
    VGP_PUSHCC(VgpPrintXPts);
 
@@ -1668,12 +1672,14 @@
    text_file = make_filename( base_dir, 
                               ( XText == clo_format ? ".txt" : ".html" ) );
 
-   fd = VG_(open)(text_file, VKI_O_CREAT|VKI_O_TRUNC|VKI_O_WRONLY,
+   sres = VG_(open)(text_file, VKI_O_CREAT|VKI_O_TRUNC|VKI_O_WRONLY,
                              VKI_S_IRUSR|VKI_S_IWUSR);
-   if (fd < 0) {
+   if (sres.isError) {
       file_err( text_file );
       VGP_POPCC(VgpPrintXPts);
       return;
+   } else {
+      fd = sres.val;
    }
 
    // Header