[project @ 2002-10-12 23:12:08 by wolfgang]
[ghc-hetmet.git] / ghc / rts / Linker.c
index 3812d72..261caf1 100644 (file)
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------------------
- * $Id: Linker.c,v 1.92 2002/06/09 19:27:16 panne Exp $
+ * $Id: Linker.c,v 1.105 2002/10/12 23:12:08 wolfgang Exp $
  *
  * (c) The GHC Team, 2000, 2001
  *
 #include <sys/types.h>
 #endif
 
+#include <stdlib.h>
+#include <string.h>
+
 #ifdef HAVE_SYS_STAT_H
 #include <sys/stat.h>
 #endif
 
-#ifdef HAVE_DLFCN_H
+#if defined(HAVE_FRAMEWORK_HASKELLSUPPORT)
+#include <HaskellSupport/dlfcn.h>
+#elif defined(HAVE_DLFCN_H)
 #include <dlfcn.h>
 #endif
 
 #elif defined(cygwin32_TARGET_OS) || defined (mingw32_TARGET_OS)
 #  define OBJFORMAT_PEi386
 #  include <windows.h>
+#  include <math.h>
+#elif defined(darwin_TARGET_OS)
+#  include <mach-o/ppc/reloc.h>
+#  define OBJFORMAT_MACHO
+#  include <mach-o/loader.h>
+#  include <mach-o/nlist.h>
+#  include <mach-o/reloc.h>
 #endif
 
 /* Hash table mapping symbol names to Symbol */
-/*Str*/HashTable *symhash;
+static /*Str*/HashTable *symhash;
 
 #if defined(OBJFORMAT_ELF)
 static int ocVerifyImage_ELF    ( ObjectCode* oc );
@@ -72,6 +84,10 @@ static int ocResolve_ELF        ( ObjectCode* oc );
 static int ocVerifyImage_PEi386 ( ObjectCode* oc );
 static int ocGetNames_PEi386    ( ObjectCode* oc );
 static int ocResolve_PEi386     ( ObjectCode* oc );
+#elif defined(OBJFORMAT_MACHO)
+static int ocVerifyImage_MachO    ( ObjectCode* oc );
+static int ocGetNames_MachO       ( ObjectCode* oc );
+static int ocResolve_MachO        ( ObjectCode* oc );
 #endif
 
 /* -----------------------------------------------------------------------------
@@ -201,7 +217,6 @@ typedef struct _RtsSymbolVal {
    executable, so we have to employ this hack. */
 #define RTS_MINGW_ONLY_SYMBOLS                  \
       SymX(memset)                              \
-      SymX(memset)                              \
       SymX(inet_ntoa)                           \
       SymX(inet_addr)                           \
       SymX(htonl)                               \
@@ -277,7 +292,6 @@ typedef struct _RtsSymbolVal {
       Maybe_ForeignObj                         \
       Maybe_Stable_Names                       \
       Sym(StgReturn)                           \
-      Sym(__stginit_GHCziPrim)                 \
       Sym(init_stack)                          \
       SymX(__stg_chk_0)                                \
       SymX(__stg_chk_1)                                \
@@ -396,7 +410,6 @@ typedef struct _RtsSymbolVal {
       SymX(rts_evalIO)                         \
       SymX(rts_evalLazyIO)                     \
       SymX(rts_eval_)                          \
-      SymX(rts_getAddr)                                \
       SymX(rts_getBool)                                \
       SymX(rts_getChar)                                \
       SymX(rts_getDouble)                      \
@@ -408,7 +421,6 @@ typedef struct _RtsSymbolVal {
       SymX(rts_getThreadId)                    \
       SymX(rts_getWord)                                \
       SymX(rts_getWord32)                      \
-      SymX(rts_mkAddr)                         \
       SymX(rts_mkBool)                         \
       SymX(rts_mkChar)                         \
       SymX(rts_mkDouble)                       \
@@ -491,6 +503,16 @@ typedef struct _RtsSymbolVal {
 /* force these symbols to be present */
 #define RTS_EXTRA_SYMBOLS                      \
       Sym(__divsf3)
+#elif defined(powerpc_TARGET_ARCH)
+#define RTS_EXTRA_SYMBOLS                      \
+      Sym(__divdi3)                             \
+      Sym(__udivdi3)                            \
+      Sym(__moddi3)                             \
+      Sym(__umoddi3)                           \
+      Sym(__ashldi3)                           \
+      Sym(__ashrdi3)                           \
+      Sym(__lshrdi3)                           \
+      Sym(__eprintf)
 #else
 #define RTS_EXTRA_SYMBOLS /* nothing */
 #endif
@@ -564,7 +586,11 @@ static void ghciInsertStrHashTable ( char* obj_name,
 /* -----------------------------------------------------------------------------
  * initialize the object linker
  */
-#if defined(OBJFORMAT_ELF)
+
+
+static int linker_init_done = 0 ;
+
+#if defined(OBJFORMAT_ELF) || defined(OBJFORMAT_MACHO)
 static void *dl_prog_handle;
 #endif
 
@@ -573,6 +599,13 @@ initLinker( void )
 {
     RtsSymbolVal *sym;
 
+    /* Make initLinker idempotent, so we can call it
+       before evey relevant operation; that means we
+       don't need to initialise the linker separately */
+    if (linker_init_done == 1) { return; } else {
+      linker_init_done = 1;
+    }
+
     symhash = allocStrHashTable();
 
     /* populate the symbol table with stuff from the RTS */
@@ -580,12 +613,15 @@ initLinker( void )
        ghciInsertStrHashTable("(GHCi built-in symbols)",
                                symhash, sym->lbl, sym->addr);
     }
-#   if defined(OBJFORMAT_ELF)
+#   if defined(OBJFORMAT_ELF) || defined(OBJFORMAT_MACHO)
     dl_prog_handle = dlopen(NULL, RTLD_LAZY);
 #   endif
 }
 
 /* -----------------------------------------------------------------------------
+ *                  Loading DLL or .so dynamic libraries
+ * -----------------------------------------------------------------------------
+ *
  * Add a DLL from which symbols may be found.  In the ELF case, just
  * do RTLD_GLOBAL-style add, so no further messing around needs to
  * happen in order that symbols in the loaded .so are findable --
@@ -594,7 +630,12 @@ initLinker( void )
  *
  * In the PEi386 case, open the DLLs and put handles to them in a
  * linked list.  When looking for a symbol, try all handles in the
- * list.
+ * list.  This means that we need to load even DLLs that are guaranteed
+ * to be in the ghc.exe image already, just so we can get a handle
+ * to give to loadSymbol, so that we can find the symbols.  For such
+ * libraries, the LoadLibrary call should be a no-op except for returning
+ * the handle.
+ * 
  */
 
 #if defined(OBJFORMAT_PEi386)
@@ -612,15 +653,16 @@ typedef
 static OpenedDLL* opened_dlls = NULL;
 #endif
 
-
-
 char *
 addDLL( char *dll_name )
 {
-#  if defined(OBJFORMAT_ELF)
+#  if defined(OBJFORMAT_ELF) || defined(OBJFORMAT_MACHO)
+   /* ------------------- ELF DLL loader ------------------- */
    void *hdl;
    char *errmsg;
 
+   initLinker();
+
    hdl= dlopen(dll_name, RTLD_NOW | RTLD_GLOBAL);
    if (hdl == NULL) {
       /* dlopen failed; return a ptr to the error msg. */
@@ -633,14 +675,15 @@ addDLL( char *dll_name )
    /*NOTREACHED*/
 
 #  elif defined(OBJFORMAT_PEi386)
+   /* ------------------- Win32 DLL loader ------------------- */
 
-   /* Add this DLL to the list of DLLs in which to search for symbols.
-      The path argument is ignored. */
    char*      buf;
    OpenedDLL* o_dll;
    HINSTANCE  instance;
 
-   /* fprintf(stderr, "\naddDLL; path=`%s', dll_name = `%s'\n", path, dll_name); */
+   initLinker();
+
+   /* fprintf(stderr, "\naddDLL; dll_name = `%s'\n", dll_name); */
 
    /* See if we've already got it, and ignore if so. */
    for (o_dll = opened_dlls; o_dll != NULL; o_dll = o_dll->next) {
@@ -648,11 +691,21 @@ addDLL( char *dll_name )
          return NULL;
    }
 
+   /* The file name has no suffix (yet) so that we can try
+      both foo.dll and foo.drv
+
+      The documentation for LoadLibrary says:
+       If no file name extension is specified in the lpFileName
+       parameter, the default library extension .dll is
+       appended. However, the file name string can include a trailing
+       point character (.) to indicate that the module name has no
+       extension. */
+
    buf = stgMallocBytes(strlen(dll_name) + 10, "addDLL");
    sprintf(buf, "%s.DLL", dll_name);
    instance = LoadLibrary(buf);
    if (instance == NULL) {
-        sprintf(buf, "%s.DRV", dll_name);              // KAA: allow loading of drivers (like winspool.drv)
+        sprintf(buf, "%s.DRV", dll_name);      // KAA: allow loading of drivers (like winspool.drv)
         instance = LoadLibrary(buf);
         if (instance == NULL) {
                free(buf);
@@ -663,6 +716,7 @@ addDLL( char *dll_name )
    }
    free(buf);
 
+   /* Add this DLL to the list of DLLs in which to search for symbols. */
    o_dll = stgMallocBytes( sizeof(OpenedDLL), "addDLL" );
    o_dll->name     = stgMallocBytes(1+strlen(dll_name), "addDLL");
    strcpy(o_dll->name, dll_name);
@@ -683,11 +737,12 @@ void *
 lookupSymbol( char *lbl )
 {
     void *val;
+    initLinker() ;
     ASSERT(symhash != NULL);
     val = lookupStrHashTable(symhash, lbl);
 
     if (val == NULL) {
-#       if defined(OBJFORMAT_ELF)
+#       if defined(OBJFORMAT_ELF) || defined(OBJFORMAT_MACHO)
        return dlsym(dl_prog_handle, lbl);
 #       elif defined(OBJFORMAT_PEi386)
         OpenedDLL* o_dll;
@@ -728,6 +783,7 @@ void *
 lookupLocalSymbol( ObjectCode* oc, char *lbl )
 {
     void *val;
+    initLinker() ;
     val = lookupStrHashTable(oc->lochash, lbl);
 
     if (val == NULL) {
@@ -752,6 +808,9 @@ void ghci_enquire ( char* addr )
    char* a;
    const int DELTA = 64;
    ObjectCode* oc;
+
+   initLinker();
+
    for (oc = objects; oc; oc = oc->next) {
       for (i = 0; i < oc->n_symbols; i++) {
          sym = oc->symbols[i];
@@ -795,6 +854,8 @@ loadObj( char *path )
    FILE *f;
 #endif
 
+   initLinker();
+
    /* fprintf(stderr, "loadObj %s\n", path ); */
 
    /* Check that we haven't already loaded this object.  Don't give up
@@ -824,6 +885,8 @@ loadObj( char *path )
    oc->formatName = "ELF";
 #  elif defined(OBJFORMAT_PEi386)
    oc->formatName = "PEi386";
+#  elif defined(OBJFORMAT_MACHO)
+   oc->formatName = "Mach-O";
 #  else
    free(oc);
    barf("loadObj: not implemented on this platform");
@@ -897,6 +960,8 @@ loadObj( char *path )
    r = ocVerifyImage_ELF ( oc );
 #  elif defined(OBJFORMAT_PEi386)
    r = ocVerifyImage_PEi386 ( oc );
+#  elif defined(OBJFORMAT_MACHO)
+   r = ocVerifyImage_MachO ( oc );
 #  else
    barf("loadObj: no verify method");
 #  endif
@@ -907,6 +972,8 @@ loadObj( char *path )
    r = ocGetNames_ELF ( oc );
 #  elif defined(OBJFORMAT_PEi386)
    r = ocGetNames_PEi386 ( oc );
+#  elif defined(OBJFORMAT_MACHO)
+   r = ocGetNames_MachO ( oc );
 #  else
    barf("loadObj: no getNames method");
 #  endif
@@ -929,12 +996,16 @@ resolveObjs( void )
     ObjectCode *oc;
     int r;
 
+    initLinker();
+
     for (oc = objects; oc; oc = oc->next) {
        if (oc->status != OBJECT_RESOLVED) {
 #           if defined(OBJFORMAT_ELF)
            r = ocResolve_ELF ( oc );
 #           elif defined(OBJFORMAT_PEi386)
            r = ocResolve_PEi386 ( oc );
+#           elif defined(OBJFORMAT_MACHO)
+           r = ocResolve_MachO ( oc );
 #           else
            barf("resolveObjs: not implemented on this platform");
 #           endif
@@ -956,6 +1027,8 @@ unloadObj( char *path )
     ASSERT(symhash != NULL);
     ASSERT(objects != NULL);
 
+    initLinker(); 
+
     prev = NULL;
     for (oc = objects; oc; prev = oc, oc = oc->next) {
        if (!strcmp(oc->fileName,path)) {
@@ -1803,7 +1876,8 @@ ocResolve_PEi386 ( ObjectCode* oc )
             if ((void*)S != NULL) goto foundit;
             (void*)S = lookupSymbol( symbol );
             if ((void*)S != NULL) goto foundit;
-            belch("%s: unknown symbol `%s'", oc->fileName, symbol);
+           /* Newline first because the interactive linker has printed "linking..." */
+            belch("\n%s: unknown symbol `%s'", oc->fileName, symbol);
             return 0;
            foundit:
          }
@@ -2115,7 +2189,9 @@ ocVerifyImage_ELF ( ObjectCode* oc )
    switch (ehdr->e_machine) {
       case EM_386:   IF_DEBUG(linker,belch( "x86" )); break;
       case EM_SPARC: IF_DEBUG(linker,belch( "sparc" )); break;
+#ifdef EM_IA_64
       case EM_IA_64: IF_DEBUG(linker,belch( "ia64" )); break;
+#endif
       default:       IF_DEBUG(linker,belch( "unknown" ));
                      belch("%s: unknown architecture", oc->fileName);
                      return 0;
@@ -2433,7 +2509,7 @@ do_Elf_Rel_relocations ( ObjectCode* oc, char* ehdrC,
 
    for (j = 0; j < nent; j++) {
       Elf_Addr offset = rtab[j].r_offset;
-      Elf_Word info   = rtab[j].r_info;
+      Elf_Addr info   = rtab[j].r_info;
 
       Elf_Addr  P  = ((Elf_Addr)targ) + offset;
       Elf_Word* pP = (Elf_Word*)P;
@@ -2499,31 +2575,32 @@ do_Elf_Rela_relocations ( ObjectCode* oc, char* ehdrC,
 {
    int j;
    char *symbol;
-   Elf_Addr* targ;
+   Elf_Addr targ;
    Elf_Rela* rtab = (Elf_Rela*) (ehdrC + shdr[shnum].sh_offset);
    int         nent = shdr[shnum].sh_size / sizeof(Elf_Rela);
    int target_shndx = shdr[shnum].sh_info;
    int symtab_shndx = shdr[shnum].sh_link;
 
    stab  = (Elf_Sym*) (ehdrC + shdr[ symtab_shndx ].sh_offset);
-   targ  = (Elf_Addr*)(ehdrC + shdr[ target_shndx ].sh_offset);
+   targ  = (Elf_Addr) (ehdrC + shdr[ target_shndx ].sh_offset);
    IF_DEBUG(linker,belch( "relocations for section %d using symtab %d",
                           target_shndx, symtab_shndx ));
 
    for (j = 0; j < nent; j++) {
 #if defined(DEBUG) || defined(sparc_TARGET_ARCH) || defined(ia64_TARGET_ARCH)
+      /* This #ifdef only serves to avoid unused-var warnings. */
       Elf_Addr  offset = rtab[j].r_offset;
+      Elf_Addr  P      = targ + offset;
 #endif
       Elf_Addr  info   = rtab[j].r_info;
       Elf_Addr  A      = rtab[j].r_addend;
       Elf_Addr  S;
       Elf_Addr  value;
 #     if defined(sparc_TARGET_ARCH)
-      /* This #ifdef only serves to avoid unused-var warnings. */
-      Elf_Word* pP = (Elf_Word*)((Elf_Addr)targ + offset);
+      Elf_Word* pP = (Elf_Word*)P;
       Elf_Word  w1, w2;
 #     elif defined(ia64_TARGET_ARCH)
-      Elf64_Xword *pP = (Elf64_Xword *)((Elf_Addr)targ + offset);
+      Elf64_Xword *pP = (Elf64_Xword *)P;
       Elf_Addr addr;
 #     endif
 
@@ -2696,7 +2773,6 @@ ocResolve_ELF ( ObjectCode* oc )
    return 1;
 }
 
-
 /*
  * IA64 specifics
  * Instructions are 41 bits long, packed into 128 bit bundles with a 5-bit template
@@ -2790,3 +2866,349 @@ ia64_reloc_pcrel21(Elf_Addr target, Elf_Addr value, ObjectCode *oc)
 #endif /* ia64 */
 
 #endif /* ELF */
+
+/* --------------------------------------------------------------------------
+ * Mach-O specifics
+ * ------------------------------------------------------------------------*/
+
+#if defined(OBJFORMAT_MACHO)
+
+/*
+  Initial support for MachO linking on Darwin/MacOS X on PowerPC chips
+  by Wolfgang Thaller (wolfgang.thaller@gmx.net)
+  
+  I hereby formally apologize for the hackish nature of this code.
+  Things that need to be done:
+  *) get common symbols and .bss sections to work properly.
+       Haskell modules seem to work, but C modules can cause problems
+  *) implement ocVerifyImage_MachO
+  *) add more sanity checks. The current code just has to segfault if there's a
+     broken .o file.
+*/
+
+static int ocVerifyImage_MachO(ObjectCode* oc)
+{
+    // FIXME: do some verifying here
+    return 1;
+}
+
+static void resolveImports(
+    ObjectCode* oc,
+    char *image,
+    struct symtab_command *symLC,
+    struct section *sect,    // ptr to lazy or non-lazy symbol pointer section
+    unsigned long *indirectSyms,
+    struct nlist *nlist)
+{
+    unsigned i;
+    
+    for(i=0;i*4<sect->size;i++)
+    {
+       // according to otool, reserved1 contains the first index into the indirect symbol table
+       struct nlist *symbol = &nlist[indirectSyms[sect->reserved1+i]];
+       char *nm = image + symLC->stroff + symbol->n_un.n_strx;
+       void *addr = NULL;
+       
+       if((symbol->n_type & N_TYPE) == N_UNDF
+           && (symbol->n_type & N_EXT) && (symbol->n_value != 0))
+           addr = (void*) (symbol->n_value);
+       else if((addr = lookupLocalSymbol(oc,nm)) != NULL)
+           ;
+       else
+           addr = lookupSymbol(nm);
+       if(!addr)
+       {
+           fprintf(stderr, "not found: %s\n", nm);
+           abort();
+       }
+       ASSERT(addr);
+       ((void**)(image + sect->offset))[i] = addr;
+    }
+}
+
+static void relocateSection(char *image, 
+    struct symtab_command *symLC, struct nlist *nlist,
+    struct section* sections, struct section *sect)
+{
+    struct relocation_info *relocs;
+    int i,n;
+    
+    if(!strcmp(sect->sectname,"__la_symbol_ptr"))
+       return;
+    else if(!strcmp(sect->sectname,"__nl_symbol_ptr"))
+       return;
+
+    n = sect->nreloc;
+    relocs = (struct relocation_info*) (image + sect->reloff);
+    
+    for(i=0;i<n;i++)
+    {
+       if(relocs[i].r_address & R_SCATTERED)
+       {
+           struct scattered_relocation_info *scat =
+               (struct scattered_relocation_info*) &relocs[i];
+           
+           if(!scat->r_pcrel)
+           {
+               if(scat->r_length == 2 && scat->r_type == GENERIC_RELOC_VANILLA)
+               {
+                   unsigned long* word = (unsigned long*) (image + sect->offset + scat->r_address);
+                   
+                   *word = scat->r_value + sect->offset + ((long) image);
+               }
+           }
+           
+           continue; // FIXME: I hope it's OK to ignore all the others.
+       }
+       else
+       {
+           struct relocation_info *reloc = &relocs[i];
+           if(reloc->r_pcrel && !reloc->r_extern)
+               continue;
+               
+           if(!reloc->r_pcrel && reloc->r_length == 2)
+           {
+               unsigned long word;
+
+               unsigned long* wordPtr = (unsigned long*) (image + sect->offset + reloc->r_address);
+               
+               if(reloc->r_type == GENERIC_RELOC_VANILLA)
+               {
+                   word = *wordPtr;
+               }
+               else if(reloc->r_type == PPC_RELOC_LO16)
+               {
+                   word = ((unsigned short*) wordPtr)[1];
+                   word |= ((unsigned long) relocs[i+1].r_address & 0xFFFF) << 16;
+               }
+               else if(reloc->r_type == PPC_RELOC_HI16)
+               {
+                   word = ((unsigned short*) wordPtr)[1] << 16;
+                   word |= ((unsigned long) relocs[i+1].r_address & 0xFFFF);
+               }
+               else if(reloc->r_type == PPC_RELOC_HA16)
+               {
+                   word = ((unsigned short*) wordPtr)[1] << 16;
+                   word += ((short)relocs[i+1].r_address & (short)0xFFFF);
+               }
+
+               if(!reloc->r_extern)
+               {
+                   long delta = 
+                       sections[reloc->r_symbolnum-1].offset
+                       - sections[reloc->r_symbolnum-1].addr
+                       + ((long) image);
+                   
+                   word += delta;
+               }
+               else
+               {
+                   struct nlist *symbol = &nlist[reloc->r_symbolnum];
+                   char *nm = image + symLC->stroff + symbol->n_un.n_strx;
+                   word = (unsigned long) (lookupSymbol(nm));
+                   ASSERT(word);
+               }
+               
+               if(reloc->r_type == GENERIC_RELOC_VANILLA)
+               {
+                   *wordPtr = word;
+                   continue;
+               }
+               else if(reloc->r_type == PPC_RELOC_LO16)
+               {
+                   ((unsigned short*) wordPtr)[1] = word & 0xFFFF;
+                   i++; continue;
+               }
+               else if(reloc->r_type == PPC_RELOC_HI16)
+               {
+                   ((unsigned short*) wordPtr)[1] = (word >> 16) & 0xFFFF;
+                   i++; continue;
+               }
+               else if(reloc->r_type == PPC_RELOC_HA16)
+               {
+                   ((unsigned short*) wordPtr)[1] = ((word >> 16) & 0xFFFF)
+                       + ((word & (1<<15)) ? 1 : 0);
+                   i++; continue;
+               }
+               continue;
+           }
+           fprintf(stderr, "unknown reloc\n");
+           abort();
+           ASSERT(2 + 2 == 5);
+       }
+    }
+}
+
+static int ocGetNames_MachO(ObjectCode* oc)
+{
+    char *image = (char*) oc->image;
+    struct mach_header *header = (struct mach_header*) image;
+    struct load_command *lc = (struct load_command*) (image + sizeof(struct mach_header));
+    unsigned i,curSymbol;
+    struct segment_command *segLC = NULL;
+    struct section *sections, *la_ptrs = NULL, *nl_ptrs = NULL;
+    struct symtab_command *symLC = NULL;
+    struct dysymtab_command *dsymLC = NULL;
+    struct nlist *nlist;
+    unsigned long commonSize = 0;
+    char    *commonStorage = NULL;
+    unsigned long commonCounter;
+
+    for(i=0;i<header->ncmds;i++)
+    {
+       if(lc->cmd == LC_SEGMENT)
+           segLC = (struct segment_command*) lc;
+       else if(lc->cmd == LC_SYMTAB)
+           symLC = (struct symtab_command*) lc;
+       else if(lc->cmd == LC_DYSYMTAB)
+           dsymLC = (struct dysymtab_command*) lc;
+       lc = (struct load_command *) ( ((char*)lc) + lc->cmdsize );
+    }
+
+    sections = (struct section*) (segLC+1); 
+    nlist = (struct nlist*) (image + symLC->symoff);
+
+    for(i=0;i<segLC->nsects;i++)
+    {
+       if(!strcmp(sections[i].sectname,"__la_symbol_ptr"))
+           la_ptrs = &sections[i];
+       else if(!strcmp(sections[i].sectname,"__nl_symbol_ptr"))
+           nl_ptrs = &sections[i];
+           
+           // for now, only add __text and __const to the sections table
+       else if(!strcmp(sections[i].sectname,"__text"))
+           addSection(oc, SECTIONKIND_CODE_OR_RODATA, 
+               (void*) (image + sections[i].offset),
+               (void*) (image + sections[i].offset + sections[i].size));
+       else if(!strcmp(sections[i].sectname,"__const"))
+           addSection(oc, SECTIONKIND_RWDATA, 
+               (void*) (image + sections[i].offset),
+               (void*) (image + sections[i].offset + sections[i].size));
+       else if(!strcmp(sections[i].sectname,"__data"))
+           addSection(oc, SECTIONKIND_RWDATA, 
+               (void*) (image + sections[i].offset),
+               (void*) (image + sections[i].offset + sections[i].size));
+    }
+
+       // count external symbols defined here
+    oc->n_symbols = 0;
+    for(i=dsymLC->iextdefsym;i<dsymLC->iextdefsym+dsymLC->nextdefsym;i++)
+    {
+       if((nlist[i].n_type & N_TYPE) == N_SECT)
+           oc->n_symbols++;
+    }
+    for(i=0;i<symLC->nsyms;i++)
+    {
+       if((nlist[i].n_type & N_TYPE) == N_UNDF
+               && (nlist[i].n_type & N_EXT) && (nlist[i].n_value != 0))
+       {
+           commonSize += nlist[i].n_value;
+           oc->n_symbols++;
+       }
+    }
+    oc->symbols = stgMallocBytes(oc->n_symbols * sizeof(char*),
+                                  "ocGetNames_MachO(oc->symbols)");
+    
+       // insert symbols into hash table
+    for(i=dsymLC->iextdefsym,curSymbol=0;i<dsymLC->iextdefsym+dsymLC->nextdefsym;i++)
+    {
+       if((nlist[i].n_type & N_TYPE) == N_SECT)
+       {
+           char *nm = image + symLC->stroff + nlist[i].n_un.n_strx;
+           ghciInsertStrHashTable(oc->fileName, symhash, nm, image + 
+               sections[nlist[i].n_sect-1].offset
+               - sections[nlist[i].n_sect-1].addr
+               + nlist[i].n_value);
+           oc->symbols[curSymbol++] = nm;
+       }
+    }
+    
+       // insert local symbols into lochash
+    for(i=dsymLC->ilocalsym;i<dsymLC->ilocalsym+dsymLC->nlocalsym;i++)
+    {
+       if((nlist[i].n_type & N_TYPE) == N_SECT)
+       {
+           char *nm = image + symLC->stroff + nlist[i].n_un.n_strx;
+           ghciInsertStrHashTable(oc->fileName, oc->lochash, nm, image + 
+               sections[nlist[i].n_sect-1].offset
+               - sections[nlist[i].n_sect-1].addr
+               + nlist[i].n_value);
+       }
+    }
+
+    
+    commonStorage = stgCallocBytes(1,commonSize,"ocGetNames_MachO(common symbols)");
+    commonCounter = (unsigned long)commonStorage;
+    for(i=0;i<symLC->nsyms;i++)
+    {
+       if((nlist[i].n_type & N_TYPE) == N_UNDF
+               && (nlist[i].n_type & N_EXT) && (nlist[i].n_value != 0))
+       {
+           char *nm = image + symLC->stroff + nlist[i].n_un.n_strx;
+           unsigned long sz = nlist[i].n_value;
+           
+           nlist[i].n_value = commonCounter;
+           
+           ghciInsertStrHashTable(oc->fileName, symhash, nm, (void*)commonCounter);
+           oc->symbols[curSymbol++] = nm;
+           
+           commonCounter += sz;
+       }
+    }
+    return 1;
+}
+
+static int ocResolve_MachO(ObjectCode* oc)
+{
+    char *image = (char*) oc->image;
+    struct mach_header *header = (struct mach_header*) image;
+    struct load_command *lc = (struct load_command*) (image + sizeof(struct mach_header));
+    unsigned i;
+    struct segment_command *segLC = NULL;
+    struct section *sections, *la_ptrs = NULL, *nl_ptrs = NULL;
+    struct symtab_command *symLC = NULL;
+    struct dysymtab_command *dsymLC = NULL;
+    struct nlist *nlist;
+    unsigned long *indirectSyms;
+
+    for(i=0;i<header->ncmds;i++)
+    {
+       if(lc->cmd == LC_SEGMENT)
+           segLC = (struct segment_command*) lc;
+       else if(lc->cmd == LC_SYMTAB)
+           symLC = (struct symtab_command*) lc;
+       else if(lc->cmd == LC_DYSYMTAB)
+           dsymLC = (struct dysymtab_command*) lc;
+       lc = (struct load_command *) ( ((char*)lc) + lc->cmdsize );
+    }
+    
+    sections = (struct section*) (segLC+1); 
+    nlist = (struct nlist*) (image + symLC->symoff);
+
+    for(i=0;i<segLC->nsects;i++)
+    {
+       if(!strcmp(sections[i].sectname,"__la_symbol_ptr"))
+           la_ptrs = &sections[i];
+       else if(!strcmp(sections[i].sectname,"__nl_symbol_ptr"))
+           nl_ptrs = &sections[i];
+    }
+    
+    indirectSyms = (unsigned long*) (image + dsymLC->indirectsymoff);
+
+    if(la_ptrs)
+       resolveImports(oc,image,symLC,la_ptrs,indirectSyms,nlist);
+    if(nl_ptrs)
+       resolveImports(oc,image,symLC,nl_ptrs,indirectSyms,nlist);
+    
+    for(i=0;i<segLC->nsects;i++)
+    {
+       relocateSection(image,symLC,nlist,sections,&sections[i]);
+    }
+
+    /* Free the local symbol table; we won't need it again. */
+    freeHashTable(oc->lochash, NULL);
+    oc->lochash = NULL;
+    return 1;
+}
+
+#endif