[PATCHv4 next] kconfig: add dependency warning print about invalid values while KBUILD_EXTRA_WARN=c

[sunying]

From: Ying Sun <sunying@xxxxxxxxxxxxxxxx>

The patch enhances kernel error messages, fixes problems with
 the previous version of v3, and has been thoroughly tested.
 We believe it will improve the clarity and usefulness
 of kconfig error messages, which will help developers better diagnose and
 resolve configuration issues.

----- v3 -> v4:
1. Fixed the dependency logic print error, distinguishing
 between unsatisfied dependencies and forced enable
 errors (related to the select keyword).
2. Add export KCONFIG_WARN_CHANGED_INPUT=1 to scripts/kconfig/Makefile,
 which can be enabled by setting KBUILD_EXTRA_WARN to -c.

Signed-off-by: Siyuan Guo <zy21df106@xxxxxxxxxxx>
Signed-off-by: Ying Sun <sunying@xxxxxxxxxxxxxxxx>
---
 scripts/kconfig/Makefile   |  1 +
 scripts/kconfig/confdata.c | 60 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index ea1bf3b3dbde..b755246fe057 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -29,6 +29,7 @@ KCONFIG_DEFCONFIG_LIST += arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)
 
 ifneq ($(findstring c, $(KBUILD_EXTRA_WARN)),)
 export KCONFIG_WARN_UNKNOWN_SYMBOLS=1
+export KCONFIG_WARN_CHANGED_INPUT=1
 endif
 
 ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index 0e35c4819cf1..91c63bd1cedd 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -176,6 +176,41 @@ static void conf_warning(const char *fmt, ...)
 	conf_warnings++;
 }
 
+static void conf_warn_unmet_rev(struct symbol *sym)
+{
+	struct gstr gs = str_new();
+
+	str_printf(&gs,
+		"WARNING: unmet reverse dependencies detected for %s\n",
+		sym->name);
+
+	expr_gstr_print_revdep(sym->rev_dep.expr, &gs, yes,
+				" Selected by [y]:\n");
+	expr_gstr_print_revdep(sym->rev_dep.expr, &gs, mod,
+				" Selected by [m]:\n");
+
+	fputs(str_get(&gs), stderr);
+	str_free(&gs);
+}
+
+static void conf_warn_dep_error(struct symbol *sym)
+{
+	struct gstr gs = str_new();
+
+	str_printf(&gs,
+		"WARNING: unmet direct dependencies detected for %s\n",
+		sym->name);
+
+	str_printf(&gs,
+		" Depends on [%c]: ",
+		sym->dir_dep.tri == mod ? 'm' : 'n');
+	expr_gstr_print(sym->dir_dep.expr, &gs);
+
+	str_printf(&gs, "\n");
+	fputs(str_get(&gs), stderr);
+	str_free(&gs);
+}
+
 static void conf_default_message_callback(const char *s)
 {
 	printf("#\n# ");
@@ -522,6 +557,31 @@ int conf_read(const char *name)
 			continue;
 		conf_unsaved++;
 		/* maybe print value in verbose mode... */
+		if (getenv("KCONFIG_WARN_CHANGED_INPUT")) {
+			if (sym->prop) {
+				switch (sym->type) {
+				case S_BOOLEAN:
+				case S_TRISTATE:
+					if (sym->def[S_DEF_USER].tri != sym_get_tristate_value(sym)) {
+						if (sym->rev_dep.tri < sym->def[S_DEF_USER].tri &&
+							sym->dir_dep.tri < sym->def[S_DEF_USER].tri)
+								conf_warn_dep_error(sym);
+						if (sym->rev_dep.tri > sym->def[S_DEF_USER].tri &&
+							sym->dir_dep.tri >= sym->def[S_DEF_USER].tri)
+								conf_warn_unmet_rev(sym);
+					}
+					break;
+				case S_INT:
+				case S_HEX:
+				case S_STRING:
+					if (sym->dir_dep.tri == no && sym_has_value(sym))
+						conf_warn_dep_error(sym);
+					break;
+				default:
+					break;
+				}
+			}
+		}
 	}
 
 	for_all_symbols(sym) {
-- 
2.43.0