Merge branch 'bjorn/improve-crash-dumps/OTP-14685' into maint

* bjorn/improve-crash-dumps/OTP-14685:
  Bump version of crash dumps to 0.4
  Verify that binaries of different sizes are dumped correctly
  Don't dump literal areas that are not referenced at all
  Dump literals separately to avoid incomplete heap data
  Implement dumping of maps in crash dumps
  Buffer writing of crash dumps

8 files changed, 430 insertions, 23 deletions

diff --git a/erts/emulator/beam/beam_ranges.c b/erts/emulator/beam/beam_ranges.c
index 9b0335e83d..fac4289271 100644
--- a/erts/emulator/beam/beam_ranges.c
+++ b/erts/emulator/beam/beam_ranges.c
@@ -32,6 +32,15 @@ typedef struct {
     erts_smp_atomic_t end; /* (BeamInstr*) Points one word beyond last function in module. */
 } Range;
 
+/*
+ * Used for crash dumping of literals. The size of erts_dump_lit_areas is
+ * always twice the number of active ranges (to allow for literals in both
+ * current and old code).
+ */
+
+ErtsLiteralArea** erts_dump_lit_areas;
+Uint erts_dump_num_lit_areas;
+
 /* Range 'end' needs to be atomic as we purge module
     by setting end=start in active code_ix */
 #define RANGE_END(R) ((BeamInstr*)erts_smp_atomic_read_nob(&(R)->end))
@@ -97,6 +106,11 @@ erts_init_ranges(void)
 	r[i].allocated = 0;
 	erts_smp_atomic_init_nob(&r[i].mid, 0);
     }
+
+    erts_dump_num_lit_areas = 8;
+    erts_dump_lit_areas = (ErtsLiteralArea **)
+        erts_alloc(ERTS_ALC_T_CRASH_DUMP,
+                   erts_dump_num_lit_areas * sizeof(ErtsLiteralArea*));
 }
 
 void
@@ -164,6 +178,14 @@ erts_end_staging_ranges(int commit)
 	erts_smp_atomic_set_nob(&r[dst].mid,
 				(erts_aint_t) (r[dst].modules +
 					       r[dst].n / 2));
+
+        if (r[dst].allocated * 2 > erts_dump_num_lit_areas) {
+            erts_dump_num_lit_areas *= 2;
+            erts_dump_lit_areas = (ErtsLiteralArea **)
+                erts_realloc(ERTS_ALC_T_CRASH_DUMP,
+                             (void *) erts_dump_lit_areas,
+                             erts_dump_num_lit_areas * sizeof(ErtsLiteralArea*));
+        }
     }
 }
 
diff --git a/erts/emulator/beam/break.c b/erts/emulator/beam/break.c
index 76a0c5c716..e57be5a595 100644
--- a/erts/emulator/beam/break.c
+++ b/erts/emulator/beam/break.c
@@ -58,6 +58,8 @@ static void dump_attributes(fmtfn_t to, void *to_arg, byte* ptr, int size);
 
 extern char* erts_system_version[];
 
+#define WRITE_BUFFER_SIZE (64*1024)
+
 static void
 port_info(fmtfn_t to, void *to_arg)
 {
@@ -677,18 +679,28 @@ bin_check(void)
 static Sint64 crash_dump_limit = ERTS_SINT64_MAX;
 static Sint64 crash_dump_written = 0;
 
-static int crash_dump_limited_writer(void* vfdp, char* buf, size_t len)
+typedef struct LimitedWriterInfo_ {
+    fmtfn_t to;
+    void* to_arg;
+} LimitedWriterInfo;
+
+static int
+crash_dump_limited_writer(void* vfdp, char* buf, size_t len)
 {
     const char stop_msg[] = "\n=abort:CRASH DUMP SIZE LIMIT REACHED\n";
+    LimitedWriterInfo* lwi = (LimitedWriterInfo *) vfdp;
 
     crash_dump_written += len;
     if (crash_dump_written <= crash_dump_limit) {
-        return erts_write_fd(vfdp, buf, len);
+        return lwi->to(lwi->to_arg, buf, len);
     }
 
     len -= (crash_dump_written - crash_dump_limit);
-    erts_write_fd(vfdp, buf, len);
-    erts_write_fd(vfdp, (char*)stop_msg, sizeof(stop_msg)-1);
+    lwi->to(lwi->to_arg, buf, len);
+    lwi->to(lwi->to_arg, (char*)stop_msg, sizeof(stop_msg)-1);
+    if (lwi->to == &erts_write_fp) {
+        fclose((FILE *) lwi->to_arg);
+    }
 
     /* We assume that crash dump was called from erts_exit_vv() */
     erts_exit_epilogue();
@@ -713,6 +725,9 @@ erl_crash_dump_v(char *file, int line, char* fmt, va_list args)
     int i;
     fmtfn_t to = &erts_write_fd;
     void*   to_arg;
+    FILE* fp = 0;
+    LimitedWriterInfo lwi;
+    static char* write_buffer;  /* 'static' to avoid a leak warning in valgrind */
 
     if (ERTS_SOMEONE_IS_CRASH_DUMPING)
 	return;
@@ -820,9 +835,30 @@ erl_crash_dump_v(char *file, int line, char* fmt, va_list args)
     fd = open(dumpname,O_WRONLY | O_CREAT | O_TRUNC,0640);
     if (fd < 0)
 	return; /* Can't create the crash dump, skip it */
-    to_arg = (void*)&fd;
+
+    /*
+     * Wrap into a FILE* so that we can use buffered output. Set an
+     * explicit buffer to make sure the first write does not fail because
+     * of a failure to allocate a buffer.
+     */
+    write_buffer = (char *) erts_alloc_fnf(ERTS_ALC_T_TMP, WRITE_BUFFER_SIZE);
+    if (write_buffer && (fp = fdopen(fd, "w")) != NULL) {
+        setvbuf(fp, write_buffer, _IOFBF, WRITE_BUFFER_SIZE);
+        lwi.to = &erts_write_fp;
+        lwi.to_arg = (void*)fp;
+    } else {
+        lwi.to = &erts_write_fd;
+        lwi.to_arg = (void*)&fd;
+    }
+    if (to == &crash_dump_limited_writer) {
+        to_arg = (void *) &lwi;
+    } else {
+        to = lwi.to;
+        to_arg = lwi.to_arg;
+    }
+
     time(&now);
-    erts_cbprintf(to, to_arg, "=erl_crash_dump:0.3\n%s", ctime(&now));
+    erts_cbprintf(to, to_arg, "=erl_crash_dump:0.4\n%s", ctime(&now));
 
     if (file != NULL)
        erts_cbprintf(to, to_arg, "The error occurred in file %s, line %d\n", file, line);
@@ -932,6 +968,9 @@ erl_crash_dump_v(char *file, int line, char* fmt, va_list args)
     }
 
     erts_cbprintf(to, to_arg, "=end\n");
+    if (fp) {
+        fclose(fp);
+    }
     close(fd);
     erts_fprintf(stderr,"done\n");
 }
diff --git a/erts/emulator/beam/erl_alloc.types b/erts/emulator/beam/erl_alloc.types
index 50a1d97dd5..252bf1cc7e 100644
--- a/erts/emulator/beam/erl_alloc.types
+++ b/erts/emulator/beam/erl_alloc.types
@@ -285,6 +285,7 @@ type    MREF_ENT	STANDARD	SYSTEM		magic_ref_entry
 type	MREF_TAB_BKTS	STANDARD	SYSTEM		magic_ref_table_buckets
 type	MREF_TAB	LONG_LIVED	SYSTEM		magic_ref_table
 type	MINDIRECTION	FIXED_SIZE	SYSTEM		magic_indirection
+type	CRASH_DUMP	STANDARD	SYSTEM		crash_dump
 
 +if threads_no_smp
 # Need thread safe allocs, but std_alloc and fix_alloc are not;
diff --git a/erts/emulator/beam/erl_process_dump.c b/erts/emulator/beam/erl_process_dump.c
index b826e6c5d3..9fd024cae8 100644
--- a/erts/emulator/beam/erl_process_dump.c
+++ b/erts/emulator/beam/erl_process_dump.c
@@ -32,6 +32,7 @@
 #include "dist.h"
 #include "beam_catches.h"
 #include "erl_binary.h"
+#include "erl_map.h"
 #define ERTS_WANT_EXTERNAL_TAGS
 #include "external.h"
 
@@ -51,6 +52,11 @@ static void print_function_from_pc(fmtfn_t to, void *to_arg, BeamInstr* x);
 static void heap_dump(fmtfn_t to, void *to_arg, Eterm x);
 static void dump_binaries(fmtfn_t to, void *to_arg, Binary* root);
 static void dump_externally(fmtfn_t to, void *to_arg, Eterm term);
+static void mark_literal(Eterm* ptr);
+static void init_literal_areas(void);
+static void dump_literals(fmtfn_t to, void *to_arg);
+static void dump_module_literals(fmtfn_t to, void *to_arg,
+                                 ErtsLiteralArea* lit_area);
 
 static Binary* all_binaries;
 
@@ -58,14 +64,14 @@ extern BeamInstr beam_apply[];
 extern BeamInstr beam_exit[];
 extern BeamInstr beam_continue_exit[];
 
-
 void
 erts_deep_process_dump(fmtfn_t to, void *to_arg)
 {
     int i, max = erts_ptab_max(&erts_proc);
 
     all_binaries = NULL;
-    
+    init_literal_areas();
+
     for (i = 0; i < max; i++) {
 	Process *p = erts_pix2proc(i);
 	if (p && p->i != ENULL) {
@@ -75,6 +81,7 @@ erts_deep_process_dump(fmtfn_t to, void *to_arg)
        }
     }
 
+    dump_literals(to, to_arg);
     dump_binaries(to, to_arg, all_binaries);
 }
 
@@ -373,7 +380,9 @@ heap_dump(fmtfn_t to, void *to_arg, Eterm x)
 	    next = (Eterm *) x;
 	} else if (is_list(x)) {
 	    ptr = list_val(x);
-	    if (ptr[0] != OUR_NIL) {
+            if (erts_is_literal(x, ptr)) {
+                mark_literal(ptr);
+            } else if (ptr[0] != OUR_NIL) {
 		erts_print(to, to_arg, PTR_FMT ":l", ptr);
 		dump_element(to, to_arg, ptr[0]);
 		erts_putc(to, to_arg, '|');
@@ -392,7 +401,9 @@ heap_dump(fmtfn_t to, void *to_arg, Eterm x)
 
 	    ptr = boxed_val(x);
 	    hdr = *ptr;
-	    if (hdr != OUR_NIL) {	/* If not visited */
+            if (erts_is_literal(x, ptr)) {
+                mark_literal(ptr);
+            } else if (hdr != OUR_NIL) {
 		erts_print(to, to_arg, PTR_FMT ":", ptr);
 	        if (is_arity_value(hdr)) {
 		    Uint i;
@@ -498,11 +509,77 @@ heap_dump(fmtfn_t to, void *to_arg, Eterm x)
 		    erts_print(to, to_arg, "p<%beu.%beu>\n",
 			       port_channel_no(x), port_number(x));
 		    *ptr = OUR_NIL;
+		} else if (is_map_header(hdr)) {
+                    if (is_flatmap_header(hdr)) {
+                        flatmap_t* fmp = (flatmap_t *) flatmap_val(x);
+                        Eterm* values = ptr + sizeof(flatmap_t) / sizeof(Eterm);
+                        Uint map_size = fmp->size;
+                        int i;
+
+                        erts_print(to, to_arg, "Mf" ETERM_FMT ":", map_size);
+                        dump_element(to, to_arg, fmp->keys);
+                        erts_putc(to, to_arg, ':');
+                        for (i = 0; i < map_size; i++) {
+                            dump_element(to, to_arg, values[i]);
+                            if (is_immed(values[i])) {
+                                values[i] = make_small(0);
+                            }
+                            if (i < map_size-1) {
+                                erts_putc(to, to_arg, ',');
+                            }
+                        }
+                        erts_putc(to, to_arg, '\n');
+                        *ptr = OUR_NIL;
+                        x = fmp->keys;
+                        if (map_size) {
+                            fmp->keys = (Eterm) next;
+                            next = &values[map_size-1];
+                        }
+                        continue;
+                    } else {
+                        Uint i;
+                        Uint sz = 0;
+                        Eterm* nodes = ptr + 1;
+
+                        switch (MAP_HEADER_TYPE(hdr)) {
+                        case MAP_HEADER_TAG_HAMT_HEAD_ARRAY:
+                            nodes++;
+                            sz = 16;
+                            erts_print(to, to_arg, "Mh" ETERM_FMT ":" ETERM_FMT ":",
+                                       hashmap_size(x), sz);
+                            break;
+                        case MAP_HEADER_TAG_HAMT_HEAD_BITMAP:
+                            nodes++;
+                            sz = hashmap_bitcount(MAP_HEADER_VAL(hdr));
+                            erts_print(to, to_arg, "Mh" ETERM_FMT ":" ETERM_FMT ":",
+                                       hashmap_size(x), sz);
+                            break;
+                        case MAP_HEADER_TAG_HAMT_NODE_BITMAP:
+                            sz = hashmap_bitcount(MAP_HEADER_VAL(hdr));
+                            erts_print(to, to_arg, "Mn" ETERM_FMT ":", sz);
+                            break;
+                        }
+                        *ptr = OUR_NIL;
+                        for (i = 0; i < sz; i++) {
+                            dump_element(to, to_arg, nodes[i]);
+                            if (is_immed(nodes[i])) {
+                                nodes[i] = make_small(0);
+                            }
+                            if (i < sz-1) {
+                                erts_putc(to, to_arg, ',');
+                            }
+                        }
+                        erts_putc(to, to_arg, '\n');
+                        x = nodes[0];
+                        nodes[0] = (Eterm) next;
+                        next = &nodes[sz-1];
+                        continue;
+                    }
 		} else {
 		    /*
 		     * All other we dump in the external term format.
 		     */
-			dump_externally(to, to_arg, x);
+                    dump_externally(to, to_arg, x);
 		    erts_putc(to, to_arg, '\n');
 		    *ptr = OUR_NIL;
 		}
@@ -564,11 +641,6 @@ dump_externally(fmtfn_t to, void *to_arg, Eterm term)
 	}
     }
 
-    /* Do not handle maps */
-    if (is_map(term)) {
-        term = am_undefined;
-    }
-
     s = p = sbuf;
     erts_encode_ext(term, &p);
     erts_print(to, to_arg, "E%X:", p-s);
@@ -577,6 +649,277 @@ dump_externally(fmtfn_t to, void *to_arg, Eterm term)
     }
 }
 
+/*
+ * Handle dumping of literal areas.
+ */
+
+static ErtsLiteralArea** lit_areas;
+static Uint num_lit_areas;
+
+static int compare_areas(const void * a, const void * b)
+{
+    ErtsLiteralArea** a_p = (ErtsLiteralArea **) a;
+    ErtsLiteralArea** b_p = (ErtsLiteralArea **) b;
+
+    if (*a_p < *b_p) {
+        return -1;
+    } else if (*b_p < *a_p) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+
+static void
+init_literal_areas(void)
+{
+    int i;
+    Module* modp;
+    ErtsCodeIndex code_ix;
+    ErtsLiteralArea** area_p;
+
+    code_ix = erts_active_code_ix();
+    erts_rlock_old_code(code_ix);
+
+    lit_areas = area_p = erts_dump_lit_areas;
+    num_lit_areas = 0;
+    for (i = 0; i < module_code_size(code_ix); i++) {
+	modp = module_code(i, code_ix);
+        if (modp == NULL) {
+            continue;
+        }
+        if (modp->curr.code_length > 0 &&
+            modp->curr.code_hdr->literal_area) {
+            *area_p++ = modp->curr.code_hdr->literal_area;
+        }
+        if (modp->old.code_length > 0 && modp->old.code_hdr->literal_area) {
+            *area_p++ = modp->old.code_hdr->literal_area;
+        }
+    }
+
+    num_lit_areas = area_p - lit_areas;
+    ASSERT(num_lit_areas <= erts_dump_num_lit_areas);
+    for (i = 0; i < num_lit_areas; i++) {
+        lit_areas[i]->off_heap = 0;
+    }
+
+    qsort(lit_areas, num_lit_areas, sizeof(ErtsLiteralArea *),
+          compare_areas);
+
+    erts_runlock_old_code(code_ix);
+}
+
+static int search_areas(const void * a, const void * b) {
+    Eterm* key = (Eterm *) a;
+    ErtsLiteralArea** b_p = (ErtsLiteralArea **) b;
+    if (key < b_p[0]->start) {
+        return -1;
+    } else if (b_p[0]->end <= key) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+static void mark_literal(Eterm* ptr)
+{
+    ErtsLiteralArea** ap;
+
+    ap = bsearch(ptr, lit_areas, num_lit_areas, sizeof(ErtsLiteralArea*),
+                 search_areas);
+    ASSERT(ap);
+    ap[0]->off_heap = (struct erl_off_heap_header *) 1;
+}
+
+
+static void
+dump_literals(fmtfn_t to, void *to_arg)
+{
+    ErtsCodeIndex code_ix;
+    int i;
+
+    code_ix = erts_active_code_ix();
+    erts_rlock_old_code(code_ix);
+
+    erts_print(to, to_arg, "=literals\n");
+    for (i = 0; i < num_lit_areas; i++) {
+        if (lit_areas[i]->off_heap) {
+            dump_module_literals(to, to_arg, lit_areas[i]);
+        }
+    }
+
+    erts_runlock_old_code(code_ix);
+}
+
+static void
+dump_module_literals(fmtfn_t to, void *to_arg, ErtsLiteralArea* lit_area)
+{
+    Eterm* htop;
+    Eterm* hend;
+
+    htop = lit_area->start;
+    hend = lit_area->end;
+    while (htop < hend) {
+        Eterm w = *htop;
+        Eterm term;
+        Uint size;
+
+        switch (primary_tag(w)) {
+        case TAG_PRIMARY_HEADER:
+            term = make_boxed(htop);
+            erts_print(to, to_arg, PTR_FMT ":", htop);
+            if (is_arity_value(w)) {
+                Uint i;
+                Uint arity = arityval(w);
+
+                erts_print(to, to_arg, "t" ETERM_FMT ":", arity);
+                for (i = 1; i <= arity; i++) {
+                    dump_element(to, to_arg, htop[i]);
+                    if (i < arity) {
+                        erts_putc(to, to_arg, ',');
+                    }
+                }
+                erts_putc(to, to_arg, '\n');
+            } else if (w == HEADER_FLONUM) {
+                FloatDef f;
+                char sbuf[31];
+                int i;
+
+                GET_DOUBLE_DATA((htop+1), f);
+                i = sys_double_to_chars(f.fd, sbuf, sizeof(sbuf));
+                sys_memset(sbuf+i, 0, 31-i);
+                erts_print(to, to_arg, "F%X:%s\n", i, sbuf);
+            } else if (_is_bignum_header(w)) {
+                erts_print(to, to_arg, "B%T\n", term);
+            } else if (is_binary_header(w)) {
+                Uint tag = thing_subtag(w);
+                Uint size = binary_size(term);
+                Uint i;
+
+                if (tag == HEAP_BINARY_SUBTAG) {
+                    byte* p;
+
+                    erts_print(to, to_arg, "Yh%X:", size);
+                    p = binary_bytes(term);
+                    for (i = 0; i < size; i++) {
+                        erts_print(to, to_arg, "%02X", p[i]);
+                    }
+                } else if (tag == REFC_BINARY_SUBTAG) {
+                    ProcBin* pb = (ProcBin *) binary_val(term);
+                    Binary* val = pb->val;
+
+                    if (erts_atomic_xchg_nob(&val->intern.refc, 0) != 0) {
+                        val->intern.flags = (UWord) all_binaries;
+                        all_binaries = val;
+                    }
+                    erts_print(to, to_arg,
+                               "Yc" PTR_FMT ":" PTR_FMT ":" PTR_FMT,
+                               val,
+                               pb->bytes - (byte *)val->orig_bytes,
+                               size);
+                } else if (tag == SUB_BINARY_SUBTAG) {
+                    ErlSubBin* Sb = (ErlSubBin *) binary_val(term);
+                    Eterm* real_bin;
+                    void* val;
+
+                    real_bin = boxed_val(Sb->orig);
+                    if (thing_subtag(*real_bin) == REFC_BINARY_SUBTAG) {
+                        /*
+                         * Unvisited REFC_BINARY: Point directly to
+                         * the binary.
+                         */
+                        ProcBin* pb = (ProcBin *) real_bin;
+                        val = pb->val;
+                    } else {
+                        /*
+                         * Heap binary or visited REFC binary: Point
+                         * to heap binary or ProcBin on the heap.
+                         */
+                        val = real_bin;
+                    }
+                    erts_print(to, to_arg,
+                               "Ys" PTR_FMT ":" PTR_FMT ":" PTR_FMT,
+                               val, Sb->offs, size);
+                }
+                erts_putc(to, to_arg, '\n');
+            } else if (is_map_header(w)) {
+                if (is_flatmap_header(w)) {
+                    flatmap_t* fmp = (flatmap_t *) flatmap_val(term);
+                    Eterm* values = htop + sizeof(flatmap_t) / sizeof(Eterm);
+                    Uint map_size = fmp->size;
+                    int i;
+
+                    erts_print(to, to_arg, "Mf" ETERM_FMT ":", map_size);
+                    dump_element(to, to_arg, fmp->keys);
+                    erts_putc(to, to_arg, ':');
+                    for (i = 0; i < map_size; i++) {
+                        dump_element(to, to_arg, values[i]);
+                        if (i < map_size-1) {
+                            erts_putc(to, to_arg, ',');
+                        }
+                    }
+                    erts_putc(to, to_arg, '\n');
+                } else {
+                    Uint i;
+                    Uint sz = 0;
+                    Eterm* nodes = htop + 1;
+
+                    switch (MAP_HEADER_TYPE(w)) {
+                    case MAP_HEADER_TAG_HAMT_HEAD_ARRAY:
+                        nodes++;
+                        sz = 16;
+                        erts_print(to, to_arg, "Mh" ETERM_FMT ":" ETERM_FMT ":",
+                                   hashmap_size(term), sz);
+                        break;
+                    case MAP_HEADER_TAG_HAMT_HEAD_BITMAP:
+                        nodes++;
+                        sz = hashmap_bitcount(MAP_HEADER_VAL(w));
+                        erts_print(to, to_arg, "Mh" ETERM_FMT ":" ETERM_FMT ":",
+                                   hashmap_size(term), sz);
+                        break;
+                    case MAP_HEADER_TAG_HAMT_NODE_BITMAP:
+                        sz = hashmap_bitcount(MAP_HEADER_VAL(w));
+                        erts_print(to, to_arg, "Mn" ETERM_FMT ":", sz);
+                        break;
+                    }
+                    for (i = 0; i < sz; i++) {
+                        dump_element(to, to_arg, nodes[i]);
+                        if (i < sz-1) {
+                            erts_putc(to, to_arg, ',');
+                        }
+                    }
+                    erts_putc(to, to_arg, '\n');
+                }
+            }
+            size = 1 + header_arity(w);
+            switch (w & _HEADER_SUBTAG_MASK) {
+            case MAP_SUBTAG:
+                if (is_flatmap_header(w)) {
+                    size += 1 + flatmap_get_size(htop);
+                } else {
+                    size += hashmap_bitcount(MAP_HEADER_VAL(w));
+                }
+                break;
+            case SUB_BINARY_SUBTAG:
+                size += 1;
+                break;
+            }
+            break;
+        default:
+            ASSERT(!is_header(htop[1]));
+            erts_print(to, to_arg, PTR_FMT ":l", htop);
+            dump_element(to, to_arg, htop[0]);
+            erts_putc(to, to_arg, '|');
+            dump_element(to, to_arg, htop[1]);
+            erts_putc(to, to_arg, '\n');
+            size = 2;
+            break;
+        }
+        htop += size;
+    }
+}
+
 void erts_dump_process_state(fmtfn_t to, void *to_arg, erts_aint32_t psflg)
 {
     char *s;
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 182d3aa44e..440723aea6 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -955,6 +955,8 @@ void erts_update_ranges(BeamInstr* code, Uint size);
 void erts_remove_from_ranges(BeamInstr* code);
 UWord erts_ranges_sz(void);
 void erts_lookup_function_info(FunctionInfo* fi, BeamInstr* pc, int full_info);
+ErtsLiteralArea** erts_dump_lit_areas;
+Uint erts_dump_num_lit_areas;
 
 /* break.c */
 void init_break_handler(void);
diff --git a/erts/emulator/beam/module.c b/erts/emulator/beam/module.c
index 7987cb2eb5..a386407ec2 100644
--- a/erts/emulator/beam/module.c
+++ b/erts/emulator/beam/module.c
@@ -256,4 +256,3 @@ void module_end_staging(int commit)
 
     IF_DEBUG(dbg_load_code_ix = -1);
 }
-
diff --git a/erts/include/internal/erl_printf.h b/erts/include/internal/erl_printf.h
index f180a53f18..7e9807f6a8 100644
--- a/erts/include/internal/erl_printf.h
+++ b/erts/include/internal/erl_printf.h
@@ -44,6 +44,7 @@ struct erts_dsprintf_buf_t_ {
 typedef int (*fmtfn_t)(void*, char*, size_t);
 
 int erts_write_fd(void *vfdp, char* buf, size_t len);
+int erts_write_fp(void *vfdp, char* buf, size_t len);
 int erts_write_ds(void *vdsbufp, char* buf, size_t len);
 
 int erts_printf(const char *, ...);
diff --git a/erts/lib_src/common/erl_printf.c b/erts/lib_src/common/erl_printf.c
index 7781fc2196..3b073bcd1b 100644
--- a/erts/lib_src/common/erl_printf.c
+++ b/erts/lib_src/common/erl_printf.c
@@ -147,8 +147,8 @@ write_f_add_cr(void *vfp, char* buf, size_t len)
     return len;
 }
 
-static int
-write_f(void *vfp, char* buf, size_t len)
+int
+erts_write_fp(void *vfp, char* buf, size_t len)
 {
     ASSERT(vfp);
 #ifdef PUTC_ON_SMALL_WRITES
@@ -257,7 +257,7 @@ erts_printf(const char *format, ...)
 	FLOCKFILE(stdout);
 	res = erts_printf_format(erts_printf_add_cr_to_stdout
 				 ? write_f_add_cr
-				 : write_f,
+				 : erts_write_fp,
 				 (void *) stdout,
 				 (char *) format,
 				 arglist);
@@ -285,7 +285,7 @@ erts_fprintf(FILE *filep, const char *format, ...)
 	else if (erts_printf_add_cr_to_stderr && filep == stderr)
 	    fmt_f = write_f_add_cr;
 	else
-	    fmt_f = write_f;
+	    fmt_f = erts_write_fp;
 	FLOCKFILE(filep);
 	res = erts_printf_format(fmt_f,(void *)filep,(char *)format,arglist);
 	FUNLOCKFILE(filep);
@@ -390,7 +390,7 @@ erts_vprintf(const char *format, va_list arglist)
 	errno = 0;
 	res = erts_printf_format(erts_printf_add_cr_to_stdout
 				 ? write_f_add_cr
-				 : write_f,
+				 : erts_write_fp,
 				 (void *) stdout,
 				 (char *) format,
 				 arglist);
@@ -414,7 +414,7 @@ erts_vfprintf(FILE *filep, const char *format, va_list arglist)
 	else if (erts_printf_add_cr_to_stderr && filep == stderr)
 	    fmt_f = write_f_add_cr;
 	else
-	    fmt_f = write_f;
+	    fmt_f = erts_write_fp;
 	res = erts_printf_format(fmt_f,(void *)filep,(char *)format,arglist);
     }
     return res;