Fix for #4318 (Linker failure on OS X 10.6)
[ghc-hetmet.git] / rts / Linker.c
index cfec769..4b984da 100644 (file)
@@ -119,7 +119,8 @@ static /*Str*/HashTable *stablehash;
 ObjectCode *objects = NULL;    /* initially empty */
 
 static HsInt loadOc( ObjectCode* oc );
-static ObjectCode* mkOc( char *path, char *image, int imageSize
+static ObjectCode* mkOc( char *path, char *image, int imageSize,
+                         char *archiveMemberName
 #ifndef USE_MMAP
 #ifdef darwin_HOST_OS
                        , int misalignment
@@ -354,15 +355,6 @@ typedef struct _RtsSymbolVal {
 #define RTS_POSIX_ONLY_SYMBOLS  /**/
 #define RTS_CYGWIN_ONLY_SYMBOLS /**/
 
-/* Extra syms gen'ed by mingw-2's gcc-3.2: */
-#if __GNUC__>=3
-#define RTS_MINGW_EXTRA_SYMS                    \
-      SymI_NeedsProto(_imp____mb_cur_max)       \
-      SymI_NeedsProto(_imp___pctype)
-#else
-#define RTS_MINGW_EXTRA_SYMS
-#endif
-
 #if HAVE_GETTIMEOFDAY
 #define RTS_MINGW_GETTIMEOFDAY_SYM SymI_NeedsProto(gettimeofday)
 #else
@@ -463,11 +455,14 @@ typedef struct _RtsSymbolVal {
       SymI_NeedsProto(opendir)                           \
       SymI_NeedsProto(readdir)                           \
       SymI_NeedsProto(rewinddir)                         \
-      RTS_MINGW_EXTRA_SYMS                               \
+      SymI_NeedsProto(_imp____mb_cur_max)               \
+      SymI_NeedsProto(_imp___pctype)                    \
+      SymI_NeedsProto(__chkstk)                                 \
       RTS_MINGW_GETTIMEOFDAY_SYM                        \
       SymI_NeedsProto(closedir)
 #endif
 
+
 #if defined(darwin_HOST_OS) && HAVE_PRINTF_LDBLSTUB
 #define RTS_DARWIN_ONLY_SYMBOLS                                    \
      SymI_NeedsProto(asprintf$LDBLStub)                     \
@@ -1140,11 +1135,16 @@ initLinker( void )
     int compileResult;
 #endif
 
+    IF_DEBUG(linker, debugBelch("initLinker: start\n"));
+
     /* 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;
+    if (linker_init_done == 1) { 
+       IF_DEBUG(linker, debugBelch("initLinker: idempotent return\n"));
+       return;
+    } else {
+        linker_init_done = 1;
     }
 
 #if defined(THREADED_RTS) && (defined(OBJFORMAT_ELF) || defined(OBJFORMAT_MACHO))
@@ -1157,6 +1157,7 @@ initLinker( void )
     for (sym = rtsSyms; sym->lbl != NULL; sym++) {
        ghciInsertStrHashTable("(GHCi built-in symbols)",
                                symhash, sym->lbl, sym->addr);
+       IF_DEBUG(linker, debugBelch("initLinker: inserting rts symbol %s, %p\n", sym->lbl, sym->addr));
     }
 #   if defined(OBJFORMAT_MACHO) && defined(powerpc_HOST_ARCH)
     machoInitSymbolsWithoutUnderscore();
@@ -1195,6 +1196,9 @@ initLinker( void )
     addDLL("msvcrt");
     addDLL("kernel32");
 #endif
+
+    IF_DEBUG(linker, debugBelch("initLinker: done\n"));
+    return;
 }
 
 void
@@ -1449,11 +1453,13 @@ void *
 lookupSymbol( char *lbl )
 {
     void *val;
+    IF_DEBUG(linker, debugBelch("lookupSymbol: looking up %s\n", lbl));
     initLinker() ;
     ASSERT(symhash != NULL);
     val = lookupStrHashTable(symhash, lbl);
 
     if (val == NULL) {
+       IF_DEBUG(linker, debugBelch("lookupSymbol: symbol not found\n"));
 #       if defined(OBJFORMAT_ELF)
        return dlsym(dl_prog_handle, lbl);
 #       elif defined(OBJFORMAT_MACHO)
@@ -1466,6 +1472,7 @@ lookupSymbol( char *lbl )
                  symbol name. For now, we simply strip it off here (and ONLY
                  here).
         */
+        IF_DEBUG(linker, debugBelch("lookupSymbol: looking up %s with dlsym\n", lbl));
         ASSERT(lbl[0] == '_');
         return dlsym(dl_prog_handle, lbl+1);
 #       else
@@ -1494,6 +1501,7 @@ lookupSymbol( char *lbl )
         return NULL;
 #       endif
     } else {
+       IF_DEBUG(linker, debugBelch("lookupSymbol: value of %s is %p\n", lbl, val));
        return val;
     }
 }
@@ -1608,7 +1616,8 @@ mmap_again:
 #endif // USE_MMAP
 
 static ObjectCode*
-mkOc( char *path, char *image, int imageSize
+mkOc( char *path, char *image, int imageSize,
+      char *archiveMemberName
 #ifndef USE_MMAP
 #ifdef darwin_HOST_OS
     , int misalignment
@@ -1632,10 +1641,17 @@ mkOc( char *path, char *image, int imageSize
 
    oc->image = image;
    /* sigh, strdup() isn't a POSIX function, so do it the long way */
-   /* XXX What should this be for an archive? */
    oc->fileName = stgMallocBytes( strlen(path)+1, "loadObj" );
    strcpy(oc->fileName, path);
 
+   if (archiveMemberName) {
+       oc->archiveMemberName = stgMallocBytes( strlen(archiveMemberName)+1, "loadObj" );
+       strcpy(oc->archiveMemberName, archiveMemberName);
+   }
+   else {
+       oc->archiveMemberName = NULL;
+   }
+
    oc->fileSize          = imageSize;
    oc->symbols           = NULL;
    oc->sections          = NULL;
@@ -1663,8 +1679,16 @@ loadArchive( char *path )
    int imageSize;
    FILE *f;
    int n;
-   char tmp[16];
+   size_t fileNameSize;
+   char *file;
+   size_t fileSize;
    int isObject;
+   char tmp[12];
+
+   IF_DEBUG(linker, debugBelch("loadArchive `%s'\n", path));
+
+   fileSize = 32;
+   file = stgMallocBytes(fileSize, "loadArchive(file)");
 
    f = fopen(path, "rb");
    if (!f)
@@ -1675,7 +1699,7 @@ loadArchive( char *path )
        barf("loadArchive: Not an archive: `%s'", path);
 
    while(1) {
-       n = fread ( tmp, 1, 16, f );
+       n = fread ( file, 1, 16, f );
        if (n != 16) {
            if (feof(f)) {
                break;
@@ -1684,14 +1708,6 @@ loadArchive( char *path )
                barf("loadArchive: Failed reading file name from `%s'", path);
            }
        }
-       /* Ignore special files */
-       if ((0 == strncmp(tmp, "/               ", 16)) ||
-           (0 == strncmp(tmp, "//              ", 16))) {
-           isObject = 0;
-       }
-       else {
-           isObject = 1;
-       }
        n = fread ( tmp, 1, 12, f );
        if (n != 12)
            barf("loadArchive: Failed reading mod time from `%s'", path);
@@ -1715,7 +1731,38 @@ loadArchive( char *path )
        if (strncmp(tmp, "\x60\x0A", 2) != 0)
            barf("loadArchive: Failed reading magic from `%s' at %ld. Got %c%c", path, ftell(f), tmp[0], tmp[1]);
 
+       /* Check for BSD-variant large filenames */
+       if (0 == strncmp(file, "#1/", 3)) {
+           file[16] = '\0';
+           for (n = 3; isdigit(file[n]); n++);
+           file[n] = '\0';
+           fileNameSize = atoi(file + 3);
+           imageSize -= fileNameSize;
+           if (fileNameSize > fileSize) {
+               /* Double it to avoid potentially continually
+                  increasing it by 1 */
+               fileSize = fileNameSize * 2;
+               file = stgReallocBytes(file, fileSize, "loadArchive(file)");
+           }
+           n = fread ( file, 1, fileNameSize, f );
+           if (n != (int)fileNameSize)
+               barf("loadArchive: Failed reading filename from `%s'", path);
+       }
+       else {
+           fileNameSize = 16;
+       }
+
+       isObject = 0;
+       for (n = 0; n < (int)fileNameSize - 1; n++) {
+           if ((file[n] == '.') && (file[n + 1] == 'o')) {
+               isObject = 1;
+               break;
+           }
+       }
+
        if (isObject) {
+           char *archiveMemberName;
+
            /* We can't mmap from the archive directly, as object
               files need to be 8-byte aligned but files in .ar
               archives are 2-byte aligned, and if we malloc the
@@ -1726,21 +1773,29 @@ loadArchive( char *path )
            n = fread ( image, 1, imageSize, f );
            if (n != imageSize)
                barf("loadObj: error whilst reading `%s'", path);
-           oc = mkOc(path, image, imageSize
+
+           archiveMemberName = stgMallocBytes(strlen(path) + fileNameSize + 3, "loadArchive(file)");
+           sprintf(archiveMemberName, "%s(%.*s)", path, (int)fileNameSize, file);
+
+           oc = mkOc(path, image, imageSize, archiveMemberName
 #ifndef USE_MMAP
 #ifdef darwin_HOST_OS
                     , 0
 #endif
 #endif
                     );
+
+           stgFree(archiveMemberName);
+
            if (0 == loadOc(oc)) {
+               stgFree(file);
                return 0;
            }
        }
        else {
            n = fseek(f, imageSize, SEEK_CUR);
            if (n != 0)
-               barf("loadArchive: error whilst seeking to %d in `%s'",
+               barf("loadArchive: error whilst seeking by %d in `%s'",
                     imageSize, path);
        }
        /* .ar files are 2-byte aligned */
@@ -1759,6 +1814,7 @@ loadArchive( char *path )
 
    fclose(f);
 
+   stgFree(file);
    return 1;
 }
 #else
@@ -1874,7 +1930,7 @@ loadObj( char *path )
    fclose(f);
 #endif /* USE_MMAP */
 
-   oc = mkOc(path, image, fileSize
+   oc = mkOc(path, image, fileSize, NULL
 #ifndef USE_MMAP
 #ifdef darwin_HOST_OS
             , misalignment
@@ -1889,6 +1945,8 @@ static HsInt
 loadOc( ObjectCode* oc ) {
    int r;
 
+   IF_DEBUG(linker, debugBelch("loadOc\n"));
+
 #  if defined(OBJFORMAT_MACHO) && (defined(powerpc_HOST_ARCH) || defined(x86_64_HOST_ARCH))
    r = ocAllocateSymbolExtras_MachO ( oc );
    if (!r) {
@@ -1935,6 +1993,7 @@ loadOc( ObjectCode* oc ) {
 
    /* loaded, but not resolved yet */
    oc->status = OBJECT_LOADED;
+   IF_DEBUG(linker, debugBelch("loadObj done.\n"));
 
    return 1;
 }
@@ -1950,6 +2009,7 @@ resolveObjs( void )
     ObjectCode *oc;
     int r;
 
+    IF_DEBUG(linker, debugBelch("resolveObjs: start\n"));
     initLinker();
 
     for (oc = objects; oc; oc = oc->next) {
@@ -1967,6 +2027,7 @@ resolveObjs( void )
            oc->status = OBJECT_RESOLVED;
        }
     }
+    IF_DEBUG(linker, debugBelch("resolveObjs: done\n"));
     return 1;
 }
 
@@ -1977,6 +2038,7 @@ HsInt
 unloadObj( char *path )
 {
     ObjectCode *oc, *prev;
+    HsBool unloadedAnyObj = HS_BOOL_FALSE;
 
     ASSERT(symhash != NULL);
     ASSERT(objects != NULL);
@@ -2016,12 +2078,20 @@ unloadObj( char *path )
            stgFree(oc->symbols);
            stgFree(oc->sections);
            stgFree(oc);
-           return 1;
+
+            /* This could be a member of an archive so continue
+             * unloading other members. */
+            unloadedAnyObj = HS_BOOL_TRUE;
        }
     }
 
-    errorBelch("unloadObj: can't find `%s' to unload", path);
-    return 0;
+    if (unloadedAnyObj) {
+        return 1;
+    }
+    else {
+        errorBelch("unloadObj: can't find `%s' to unload", path);
+        return 0;
+    }
 }
 
 /* -----------------------------------------------------------------------------
@@ -2033,7 +2103,7 @@ static void addProddableBlock ( ObjectCode* oc, void* start, int size )
 {
    ProddableBlock* pb
       = stgMallocBytes(sizeof(ProddableBlock), "addProddableBlock");
-   /* debugBelch("aPB %p %p %d\n", oc, start, size); */
+   IF_DEBUG(linker, debugBelch("addProddableBlock %p %p %d\n", oc, start, size));
    ASSERT(size > 0);
    pb->start      = start;
    pb->size       = size;
@@ -4303,6 +4373,8 @@ static int resolveImports(
     unsigned i;
     size_t itemSize = 4;
 
+    IF_DEBUG(linker, debugBelch("resolveImports: start\n"));
+
 #if i386_HOST_ARCH
     int isJumpTable = 0;
     if(!strcmp(sect->sectname,"__jump_table"))
@@ -4320,12 +4392,16 @@ static int resolveImports(
        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))
+       IF_DEBUG(linker, debugBelch("resolveImports: resolving %s\n", nm));
+       if ((symbol->n_type & N_TYPE) == N_UNDF
+           && (symbol->n_type & N_EXT) && (symbol->n_value != 0)) {
            addr = (void*) (symbol->n_value);
-       else
+           IF_DEBUG(linker, debugBelch("resolveImports: undefined external %s has value %p\n", nm, addr));
+       } else {
            addr = lookupSymbol(nm);
-       if(!addr)
+           IF_DEBUG(linker, debugBelch("resolveImports: looking up %s, %p\n", nm, addr));
+       }
+       if (!addr)
        {
            errorBelch("\n%s: unknown symbol `%s'", oc->fileName, nm);
            return 0;
@@ -4348,6 +4424,7 @@ static int resolveImports(
         }
     }
 
+    IF_DEBUG(linker, debugBelch("resolveImports: done\n"));
     return 1;
 }
 
@@ -4358,9 +4435,11 @@ static unsigned long relocateAddress(
     unsigned long address)
 {
     int i;
-    for(i = 0; i < nSections; i++)
+    IF_DEBUG(linker, debugBelch("relocateAddress: start\n"));
+    for (i = 0; i < nSections; i++)
     {
-        if(sections[i].addr <= address
+           IF_DEBUG(linker, debugBelch("    relocating address in section %d\n", i));
+        if (sections[i].addr <= address
             && address < sections[i].addr + sections[i].size)
         {
             return (unsigned long)oc->image
@@ -4379,7 +4458,9 @@ static int relocateSection(
     int nSections, struct section* sections, struct section *sect)
 {
     struct relocation_info *relocs;
-    int i,n;
+    int i, n;
+
+    IF_DEBUG(linker, debugBelch("relocateSection: start\n"));
 
     if(!strcmp(sect->sectname,"__la_symbol_ptr"))
        return 1;
@@ -4391,6 +4472,8 @@ static int relocateSection(
        return 1;
 
     n = sect->nreloc;
+    IF_DEBUG(linker, debugBelch("relocateSection: number of relocations: %d\n", n));
+
     relocs = (struct relocation_info*) (image + sect->reloff);
 
     for(i=0;i<n;i++)
@@ -4428,12 +4511,20 @@ static int relocateSection(
             default:
                 barf("Unknown size.");
         }
-        
-        if(type == X86_64_RELOC_GOT
+
+       IF_DEBUG(linker,
+                debugBelch("relocateSection: length = %d, thing = %d, baseValue = %p\n",
+                           reloc->r_length, thing, baseValue));
+
+        if (type == X86_64_RELOC_GOT
            || type == X86_64_RELOC_GOT_LOAD)
         {
+            struct nlist *symbol = &nlist[reloc->r_symbolnum];
+            char *nm = image + symLC->stroff + symbol->n_un.n_strx;
+
+           IF_DEBUG(linker, debugBelch("relocateSection: making jump island for %s, extern = %d, X86_64_RELOC_GOT\n", nm, reloc->r_extern));
             ASSERT(reloc->r_extern);
-            value = (uint64_t) &makeSymbolExtra(oc, reloc->r_symbolnum, value)->addr;
+            value = (uint64_t) &makeSymbolExtra(oc, reloc->r_symbolnum, (unsigned long)lookupSymbol(nm))->addr;
             
             type = X86_64_RELOC_SIGNED;
         }
@@ -4441,11 +4532,21 @@ static int relocateSection(
         {
             struct nlist *symbol = &nlist[reloc->r_symbolnum];
             char *nm = image + symLC->stroff + symbol->n_un.n_strx;
-            if(symbol->n_value == 0)
-                value = (uint64_t) lookupSymbol(nm);
-            else
+
+           IF_DEBUG(linker, debugBelch("relocateSection: looking up external symbol %s\n", nm));
+           IF_DEBUG(linker, debugBelch("               : type  = %d\n", symbol->n_type));
+           IF_DEBUG(linker, debugBelch("               : sect  = %d\n", symbol->n_sect));
+           IF_DEBUG(linker, debugBelch("               : desc  = %d\n", symbol->n_desc));
+           IF_DEBUG(linker, debugBelch("               : value = %d\n", symbol->n_value));
+            if ((symbol->n_type & N_TYPE) == N_SECT) {
                 value = relocateAddress(oc, nSections, sections,
                                         symbol->n_value);
+               IF_DEBUG(linker, debugBelch("relocateSection, defined external symbol %s, relocated address %p\n", nm, value));
+           }
+            else {
+                value = (uint64_t) lookupSymbol(nm);
+               IF_DEBUG(linker, debugBelch("relocateSection: external symbol %s, address %p\n", nm, value));
+           }
         }
         else
         {
@@ -4453,8 +4554,10 @@ static int relocateSection(
                   - sections[reloc->r_symbolnum-1].addr
                  + (uint64_t) image;
         }
-        
-        if(type == X86_64_RELOC_BRANCH)
+      
+       IF_DEBUG(linker, debugBelch("relocateSection: value = %p\n", value));
+
+        if (type == X86_64_RELOC_BRANCH)
         {
             if((int32_t)(value - baseValue) != (int64_t)(value - baseValue))
             {
@@ -4604,7 +4707,9 @@ static int relocateSection(
                              "scattered relocation entry: "
                               "object file %s; entry type %ld; "
                               "address %#lx\n", 
-                              oc->fileName, scat->r_type, scat->r_address);
+                              OC_INFORMATIVE_FILENAME(oc),
+                              scat->r_type,
+                              scat->r_address);
                         return 0;
                      }
 
@@ -4641,7 +4746,9 @@ static int relocateSection(
                         "with this r_length tag: "
                          "object file %s; entry type %ld; "
                          "r_length tag %ld; address %#lx\n", 
-                         oc->fileName, scat->r_type, scat->r_length,
+                         OC_INFORMATIVE_FILENAME(oc),
+                         scat->r_type,
+                         scat->r_length,
                          scat->r_address);
                     return 0;
                }
@@ -4651,7 +4758,9 @@ static int relocateSection(
                barf("Don't know how to handle *PC-relative* Mach-O "
                     "scattered relocation entry: "
                      "object file %s; entry type %ld; address %#lx\n", 
-                     oc->fileName, scat->r_type, scat->r_address);
+                     OC_INFORMATIVE_FILENAME(oc),
+                     scat->r_type,
+                     scat->r_address);
                return 0;
            }
 
@@ -4705,8 +4814,10 @@ static int relocateSection(
                 {
                     barf("Can't handle this Mach-O relocation entry "
                         "(not scattered): "
-                         "object file %s; entry type %ld; address %#lx\n", 
-                         oc->fileName, reloc->r_type, reloc->r_address);
+                         "object file %s; entry type %ld; address %#lx\n",
+                         OC_INFORMATIVE_FILENAME(oc),
+                         reloc->r_type,
+                         reloc->r_address);
                     return 0;
                 }
 
@@ -4780,20 +4891,32 @@ static int relocateSection(
                }
                else if(reloc->r_type == PPC_RELOC_BR24)
                {
-                    if((long)word > (long)0x01FFFFFF || (long)word < (long)0xFFE00000)
+                    if((word & 0x03) != 0)
+                        barf("%s: unconditional relative branch with a displacement "
+                             "which isn't a multiple of 4 bytes: %#lx",
+                             OC_INFORMATIVE_FILENAME(oc),
+                             word);
+
+                    if((word & 0xFE000000) != 0xFE000000 &&
+                       (word & 0xFE000000) != 0x00000000)
                     {
                         // The branch offset is too large.
                         // Therefore, we try to use a jump island.
                         if(jumpIsland == 0)
                         {
-                            barf("unconditional relative branch out of range: "
-                                 "no jump island available");
+                            barf("%s: unconditional relative branch out of range: "
+                                 "no jump island available: %#lx",
+                                 OC_INFORMATIVE_FILENAME(oc),
+                                 word);
                         }
                         
                         word = offsetToJumpIsland;
-                        if((long)word > (long)0x01FFFFFF || (long)word < (long)0xFFE00000)
-                            barf("unconditional relative branch out of range: "
-                                 "jump island out of range");
+                        if((word & 0xFE000000) != 0xFE000000 &&
+                           (word & 0xFE000000) != 0x00000000)
+                            barf("%s: unconditional relative branch out of range: "
+                                 "jump island out of range: %#lx",
+                                 OC_INFORMATIVE_FILENAME(oc),
+                                 word);
                     }
                    *wordPtr = (*wordPtr & 0xFC000003) | (word & 0x03FFFFFC);
                    continue;
@@ -4805,14 +4928,17 @@ static int relocateSection(
                 barf("Can't handle Mach-O relocation entry (not scattered) "
                       "with this r_length tag: "
                       "object file %s; entry type %ld; "
-                      "r_length tag %ld; address %#lx\n", 
-                      oc->fileName, reloc->r_type, reloc->r_length,
+                      "r_length tag %ld; address %#lx\n",
+                      OC_INFORMATIVE_FILENAME(oc),
+                      reloc->r_type,
+                      reloc->r_length,
                       reloc->r_address);
                 return 0;
            }
        }
 #endif
     }
+    IF_DEBUG(linker, debugBelch("relocateSection: done\n"));
     return 1;
 }
 
@@ -4830,6 +4956,8 @@ static int ocGetNames_MachO(ObjectCode* oc)
     char    *commonStorage = NULL;
     unsigned long commonCounter;
 
+    IF_DEBUG(linker,debugBelch("ocGetNames_MachO: start\n"));
+
     for(i=0;i<header->ncmds;i++)
     {
        if(lc->cmd == LC_SEGMENT || lc->cmd == LC_SEGMENT_64)
@@ -4848,7 +4976,8 @@ static int ocGetNames_MachO(ObjectCode* oc)
 
     for(i=0;i<segLC->nsects;i++)
     {
-        if(sections[i].size == 0)
+       IF_DEBUG(linker, debugBelch("ocGetNames_MachO: segment %d\n"));
+        if (sections[i].size == 0)
             continue;
 
         if((sections[i].flags & SECTION_TYPE) == S_ZEROFILL)
@@ -4901,6 +5030,7 @@ static int ocGetNames_MachO(ObjectCode* oc)
             }
         }
     }
+    IF_DEBUG(linker, debugBelch("ocGetNames_MachO: %d external symbols\n", oc->n_symbols));
     oc->symbols = stgMallocBytes(oc->n_symbols * sizeof(char*),
                                   "ocGetNames_MachO(oc->symbols)");
 
@@ -4915,10 +5045,13 @@ static int ocGetNames_MachO(ObjectCode* oc)
                 if(nlist[i].n_type & N_EXT)
                 {
                     char *nm = image + symLC->stroff + nlist[i].n_un.n_strx;
-                    if((nlist[i].n_desc & N_WEAK_DEF) && lookupSymbol(nm))
-                        ; // weak definition, and we already have a definition
+                    if ((nlist[i].n_desc & N_WEAK_DEF) && lookupSymbol(nm)) {
+                        // weak definition, and we already have a definition
+                       IF_DEBUG(linker, debugBelch("    weak: %s\n", nm));
+                   }
                     else
                     {
+                           IF_DEBUG(linker, debugBelch("ocGetNames_MachO: inserting %s\n", nm));
                             ghciInsertStrHashTable(oc->fileName, symhash, nm,
                                                     image
                                                     + sections[nlist[i].n_sect-1].offset
@@ -4945,6 +5078,7 @@ static int ocGetNames_MachO(ObjectCode* oc)
 
                nlist[i].n_value = commonCounter;
 
+               IF_DEBUG(linker, debugBelch("ocGetNames_MachO: inserting common symbol: %s\n", nm));
                ghciInsertStrHashTable(oc->fileName, symhash, nm,
                                       (void*)commonCounter);
                oc->symbols[curSymbol++] = nm;
@@ -4968,7 +5102,8 @@ static int ocResolve_MachO(ObjectCode* oc)
     struct dysymtab_command *dsymLC = NULL;
     struct nlist *nlist;
 
-    for(i=0;i<header->ncmds;i++)
+    IF_DEBUG(linker, debugBelch("ocResolve_MachO: start\n"));
+    for (i = 0; i < header->ncmds; i++)
     {
        if(lc->cmd == LC_SEGMENT || lc->cmd == LC_SEGMENT_64)
            segLC = (struct segment_command*) lc;
@@ -4988,7 +5123,8 @@ static int ocResolve_MachO(ObjectCode* oc)
         unsigned long *indirectSyms
             = (unsigned long*) (image + dsymLC->indirectsymoff);
 
-        for(i=0;i<segLC->nsects;i++)
+       IF_DEBUG(linker, debugBelch("ocResolve_MachO: resolving dsymLC\n"));
+        for (i = 0; i < segLC->nsects; i++)
         {
             if(    !strcmp(sections[i].sectname,"__la_symbol_ptr")
                 || !strcmp(sections[i].sectname,"__la_sym_ptr2")
@@ -5008,12 +5144,18 @@ static int ocResolve_MachO(ObjectCode* oc)
                 if(!resolveImports(oc,image,symLC,&sections[i],indirectSyms,nlist))
                     return 0;
             }
+           else
+           {
+               IF_DEBUG(linker, debugBelch("ocResolve_MachO: unknown section\n"));
+           }
         }
     }
     
     for(i=0;i<segLC->nsects;i++)
     {
-       if(!relocateSection(oc,image,symLC,nlist,segLC->nsects,sections,&sections[i]))
+           IF_DEBUG(linker, debugBelch("ocResolve_MachO: relocating section %d\n", i));
+
+       if (!relocateSection(oc,image,symLC,nlist,segLC->nsects,sections,&sections[i]))
            return 0;
     }