debug: invoke dfmt->linenum when the segment number changes

If the segment number changes, we also need to invoke dfmt->linenum(),
as a .nolist macro may end up emitting to more than one section.

This also adds the source location explicitly to the output data
structure; the cost for that is minimal, and will enable a more
sophisticated debug backend to receive the entire data structure in
the future.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>

3 files changed, 26 insertions, 11 deletions

diff --git a/asm/assemble.c b/asm/assemble.c
index e5d5682c..270262ae 100644
--- a/asm/assemble.c
+++ b/asm/assemble.c
@@ -341,8 +341,10 @@ static void warn_overflow_out(int64_t data, int size, enum out_sign sign)
  */
 static void out(struct out_data *data)
 {
-    static int32_t lineno = 0;     /* static!!! */
-    static const char *lnfname = NULL;
+    static struct last_debug_info {
+        struct src_location where;
+        int32_t segment;
+    } dbg;
     union {
         uint8_t b[8];
         uint64_t q;
@@ -398,16 +400,16 @@ static void out(struct out_data *data)
     }
 
     /*
-     * this call to src_get determines when we call the
-     * debug-format-specific "linenum" function
-     * it updates lineno and lnfname to the current values
-     * returning 0 if "same as last time", -2 if lnfname
-     * changed, and the amount by which lineno changed,
-     * if it did. thus, these variables must be static
+     * If the source location or output segment has changed,
+     * let the debug backend know.
      */
-
-    if (src_get(&lineno, &lnfname))
-        dfmt->linenum(lnfname, lineno, data->segment);
+    data->where = src_where();
+    if (!src_location_same(data->where, dbg.where) |
+        (data->segment != dbg.segment)) {
+        dbg.where   = data->where;
+        dbg.segment = data->segment;
+        dfmt->linenum(dbg.where.filename, dbg.where.lineno, data->segment);
+    }
 
     if (asize > amax) {
         if (data->type == OUT_RELADDR || data->sign == OUT_SIGNED) {
diff --git a/asm/srcfile.h b/asm/srcfile.h
index a26e1e4f..ec9965d3 100644
--- a/asm/srcfile.h
+++ b/asm/srcfile.h
@@ -43,6 +43,18 @@ struct src_location {
     const char *filename;
     int32_t lineno;
 };
+
+/*
+ * Comparing the *pointer value* of filenames is valid, because the
+ * filename hash system guarantees that each unique filename string is
+ * permanently allocated in exactly one location.
+ */
+static inline bool
+src_location_same(struct src_location here, struct src_location there)
+{
+    return here.filename == there.filename && here.lineno == there.lineno;
+}
+
 struct src_location_stack {
     struct src_location l;
     struct src_location_stack *up, *down;
diff --git a/include/nasm.h b/include/nasm.h
index efeb6190..6cffaf5d 100644
--- a/include/nasm.h
+++ b/include/nasm.h
@@ -137,6 +137,7 @@ struct out_data {
     int32_t tsegment;           /* Target segment for relocation */
     int32_t twrt;               /* Relocation with respect to */
     int64_t relbase;            /* Relative base for OUT_RELADDR */
+    struct src_location where;  /* Source file and line */
 };
 
 /*