[XEN PATCH v5 13/16] xen,symbols: rework file symbols selection

[Anthony PERARD <anthony.perard@citrix.com>]

We want to use the same rune to build mm/*/guest_*.o as the one use to
build every other *.o object. The consequence it that file symbols that
the program ./symbols prefer changes with CONFIG_ENFORCE_UNIQUE_SYMBOLS=y.

For example, when building arch/x86/mm/guest_walk_2.o from guest_walk.c,
this would be the difference of file symbol present in the object when
building with CONFIG_ENFORCE_UNIQUE_SYMBOLS=y:

(1) Currently we have those two file symbols:
    guest_walk.c
    guest_walk_2.o
(2) When building with the same rune, we will have:
    arch/x86/mm/guest_walk.c
    guest_walk_2.o

The order in which those symbols are present may be different. Building
without CONFIG_ENFORCE_UNIQUE_SYMBOLS will result in (1).

Currently, in case (1) ./symbols chooses the *.o symbol (object file
name). But in case (2), may choose the *.c symbol (source file name with
path component) if it is first

We want to have ./symbols choose the object file name symbol in both
cases. So this patch changes that ./symbols prefer the "object file
name" symbol over the "source file name with path component" symbols.

The new intended order of preference is:
    - first object file name symbol (present only in object files
      produced from multiply-compiled sources)
    - first source file name with path components symbol
    - last source file name without any path component symbol

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---

Notes:
    v5:
    - reword part of the commit message
    
    v4:
    - rescope enum symbol_type
    - remove setting values to enums, as it's not needed.
    - rename the enumeration symbols

 xen/tools/symbols.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/xen/tools/symbols.c b/xen/tools/symbols.c
index 9f9e2c990061..b3a9465b32d3 100644
--- a/xen/tools/symbols.c
+++ b/xen/tools/symbols.c
@@ -84,7 +84,12 @@ static int read_symbol(FILE *in, struct sym_entry *s)
 {
 	char str[500], type[20] = "";
 	char *sym, stype;
-	static enum { symbol, single_source, multi_source } last;
+	static enum symbol_type {
+		symbol,
+		file_source,
+		path_source,
+		obj_file,
+	} last;
 	static char *filename;
 	int rc = -1;
 
@@ -125,13 +130,20 @@ static int read_symbol(FILE *in, struct sym_entry *s)
 		 * prefer the first one if that names an object file or has a
 		 * directory component (to cover multiply compiled files).
 		 */
-		bool multi = strchr(str, '/') || (sym && sym[1] == 'o');
+		enum symbol_type current;
 
-		if (multi || last != multi_source) {
+		if (sym && sym[1] == 'o')
+		    current = obj_file;
+		else if (strchr(str, '/'))
+		    current = path_source;
+		else
+		    current = file_source;
+
+		if (current > last || last == file_source) {
 			free(filename);
 			filename = *str ? strdup(str) : NULL;
+			last = current;
 		}
-		last = multi ? multi_source : single_source;
 		goto skip_tail;
 	}
 
-- 
Anthony PERARD