/***********************************************************************/ /* */ /* Objective Caml */ /* */ /* Xavier Leroy, projet Gallium, INRIA Rocquencourt */ /* */ /* Copyright 2006 Institut National de Recherche en Informatique et */ /* en Automatique. All rights reserved. This file is distributed */ /* under the terms of the GNU Library General Public License, with */ /* the special exception on linking described in file ../LICENSE. */ /* */ /***********************************************************************/ /* $Id$ */ /* Stack backtrace for uncaught exceptions */ #include #include "alloc.h" #include "backtrace.h" #include "memory.h" #include "misc.h" #include "mlvalues.h" #include "stack.h" int caml_backtrace_active = 0; int caml_backtrace_pos = 0; code_t * caml_backtrace_buffer = NULL; value caml_backtrace_last_exn = Val_unit; #define BACKTRACE_BUFFER_SIZE 1024 /* Start or stop the backtrace machinery */ CAMLprim value caml_record_backtrace(value vflag) { int flag = Int_val(vflag); if (flag != caml_backtrace_active) { caml_backtrace_active = flag; caml_backtrace_pos = 0; if (flag) { caml_register_global_root(&caml_backtrace_last_exn); } else { caml_remove_global_root(&caml_backtrace_last_exn); } } return Val_unit; } /* Return the status of the backtrace machinery */ CAMLprim value caml_backtrace_status(value vunit) { return Val_bool(caml_backtrace_active); } /* Store the return addresses contained in the given stack fragment into the backtrace array */ void caml_stash_backtrace(value exn, uintnat pc, char * sp, char * trapsp) { frame_descr * d; uintnat h; if (exn != caml_backtrace_last_exn) { caml_backtrace_pos = 0; caml_backtrace_last_exn = exn; } if (caml_backtrace_buffer == NULL) { caml_backtrace_buffer = malloc(BACKTRACE_BUFFER_SIZE * sizeof(code_t)); if (caml_backtrace_buffer == NULL) return; } if (caml_frame_descriptors == NULL) caml_init_frame_descriptors(); while (1) { /* Find the descriptor corresponding to the return address */ h = Hash_retaddr(pc); while(1) { d = caml_frame_descriptors[h]; if (d == 0) return; /* can happen if some code not compiled with -g */ if (d->retaddr == pc) break; h = (h+1) & caml_frame_descriptors_mask; } /* Skip to next frame */ if (d->frame_size != 0xFFFF) { /* Regular frame, store its descriptor in the backtrace buffer */ if (caml_backtrace_pos >= BACKTRACE_BUFFER_SIZE) return; caml_backtrace_buffer[caml_backtrace_pos++] = (code_t) d; #ifndef Stack_grows_upwards sp += (d->frame_size & 0xFFFC); #else sp -= (d->frame_size & 0xFFFC); #endif pc = Saved_return_address(sp); #ifdef Mask_already_scanned pc = Mask_already_scanned(pc); #endif } else { /* Special frame marking the top of a stack chunk for an ML callback. Skip C portion of stack and continue with next ML stack chunk. */ struct caml_context * next_context = Callback_link(sp); sp = next_context->bottom_of_stack; pc = next_context->last_retaddr; /* A null sp means no more ML stack chunks; stop here. */ if (sp == NULL) return; } /* Stop when we reach the current exception handler */ #ifndef Stack_grows_upwards if (sp > trapsp) return; #else if (sp < trapsp) return; #endif } } /* Extract location information for the given frame descriptor */ struct loc_info { int loc_valid; int loc_is_raise; char * loc_filename; int loc_lnum; int loc_startchr; int loc_endchr; }; static void extract_location_info(frame_descr * d, /*out*/ struct loc_info * li) { uintnat infoptr; uint32 info1, info2; /* If no debugging information available, print nothing. When everything is compiled with -g, this corresponds to compiler-inserted re-raise operations. */ if ((d->frame_size & 1) == 0) { li->loc_valid = 0; li->loc_is_raise = 1; return; } /* Recover debugging info */ infoptr = ((uintnat) d + sizeof(char *) + sizeof(short) + sizeof(short) + sizeof(short) * d->num_live + sizeof(frame_descr *) - 1) & -sizeof(frame_descr *); info1 = ((uint32 *)infoptr)[0]; info2 = ((uint32 *)infoptr)[1]; /* Format of the two info words: llllllllllllllllllll aaaaaaaa bbbbbbbbbb nnnnnnnnnnnnnnnnnnnnnnnn kk 44 36 26 2 0 (32+12) (32+4) k ( 2 bits): 0 if it's a call, 1 if it's a raise n (24 bits): offset (in 4-byte words) of file name relative to infoptr l (20 bits): line number a ( 8 bits): beginning of character range b (10 bits): end of character range */ li->loc_valid = 1; li->loc_is_raise = (info1 & 3) != 0; li->loc_filename = (char *) infoptr + (info1 & 0x3FFFFFC); li->loc_lnum = info2 >> 12; li->loc_startchr = (info2 >> 4) & 0xFF; li->loc_endchr = ((info2 & 0xF) << 6) | (info1 >> 26); } static void print_location(struct loc_info * li, int index) { char * info; /* Ignore compiler-inserted raise */ if (!li->loc_valid) return; if (index == 0) info = "Raised at"; else if (li->loc_is_raise) info = "Re-raised at"; else info = "Called from"; fprintf (stderr, "%s file \"%s\", line %d, characters %d-%d\n", info, li->loc_filename, li->loc_lnum, li->loc_startchr, li->loc_endchr); } /* Print a backtrace */ void caml_print_exception_backtrace(void) { int i; struct loc_info li; for (i = 0; i < caml_backtrace_pos; i++) { extract_location_info((frame_descr *) (caml_backtrace_buffer[i]), &li); print_location(&li, i); } } /* Convert the backtrace to a data structure usable from Caml */ CAMLprim value caml_get_exception_backtrace(value unit) { CAMLparam0(); CAMLlocal4(res, arr, p, fname); int i; struct loc_info li; arr = caml_alloc(caml_backtrace_pos, 0); for (i = 0; i < caml_backtrace_pos; i++) { extract_location_info((frame_descr *) (caml_backtrace_buffer[i]), &li); if (li.loc_valid) { fname = caml_copy_string(li.loc_filename); p = caml_alloc_small(5, 0); Field(p, 0) = Val_bool(li.loc_is_raise); Field(p, 1) = fname; Field(p, 2) = Val_int(li.loc_lnum); Field(p, 3) = Val_int(li.loc_startchr); Field(p, 4) = Val_int(li.loc_endchr); } else { p = caml_alloc_small(1, 1); Field(p, 0) = Val_bool(li.loc_is_raise); } caml_modify(&Field(arr, i), p); } res = caml_alloc_small(1, 0); Field(res, 0) = arr; /* Some */ CAMLreturn(res); }