[PATCH] scripts/check-uapi.sh: add stgdiff support

[Giuliano Procida <gprocida@google.com>]

Hi John.

I spent a few minutes adding stgdiff support to the script. It's
really just for illustration purposes.

As I think you know, STG doesn't yet exist as a project outside of
AOSP. Nevertheless, this may be useful to you as-is.

STG has quite a different philosophy to libabigil in terms of
filtering out certain kinds of differences. Some of the things (like
enum enumerator additions) are not considered harmless. The reasoning
behind this is basically...
https://en.wikipedia.org/wiki/Covariance_and_contravariance_(computer_science)

However, it does have --ignore interface_addition (and the related
--ignore type_definition_addition) which can be used to detect whether
one ABI is a subset of another.

I am looking at adding support for macro definitions (gcc -g3) to STG
which will then let us cover significantly more of the UAPI surface.

Unfortunately, there are some headers which use anonymous enums to
define constants (e.g. and ironically BTF). ABI tracking these types
would require something a bit hacky. Or we could just name them.

Regards,
Giuliano.

Signed-off-by: Giuliano Procida <gprocida@google.com>
---
 scripts/check-uapi.sh | 102 ++++++++++++++++++++++++++++--------------
 1 file changed, 69 insertions(+), 33 deletions(-)

diff --git a/scripts/check-uapi.sh b/scripts/check-uapi.sh
index 755187f27be5..982666b48f3b 100755
--- a/scripts/check-uapi.sh
+++ b/scripts/check-uapi.sh
@@ -32,6 +32,7 @@ Options:
     -v             Verbose operation (print more information about each header being checked).
 
 Environmental args:
+    STGDIFF  Custom path to stgdiff binary - use stgdiff instead of abidiff
     ABIDIFF  Custom path to abidiff binary
     CC       C compiler (default is "gcc")
     ARCH     Target architecture of C compiler (default is host arch)
@@ -270,43 +271,78 @@ compare_abi() {
 		exit "$FAIL_COMPILE"
 	fi
 
-	local ret=0
-	"$ABIDIFF" --non-reachable-types "${past_header}.bin" "${base_header}.bin" > "$log" || ret="$?"
-	if [ "$ret" -eq 0 ]; then
-		if [ "$VERBOSE" = "true" ]; then
-			printf "No ABI differences detected in %s from %s -> %s\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
+	if [ "$STGDIFF" ]; then
+		local ret=0
+		"$STGDIFF" --types --ignore interface_addition --elf "${past_header}.bin" "${base_header}.bin" --format small --output "$log" || ret="$?"
+		if [ "$ret" -eq 0 ]; then
+			if [ "$VERBOSE" = "true" ]; then
+				printf "No ABI differences detected in %s from %s -> %s\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
+			fi
+		else
+			# stgdiff's return code can be used to determine the type of error
+			if [ $((ret & 0x1)) -gt 0 ]; then
+				eprintf "error - stgdiff failed\n"
+				exit 1
+			fi
+
+			{
+				printf "!!! ABI differences detected in %s from %s -> %s !!!\n\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
+				sed  -e 's/^/  /g' "$log"
+
+				if ! cmp "$past_header" "$base_header" > /dev/null 2>&1; then
+					printf "\nHeader file diff (after headers_install):\n"
+					diff -Naur "$past_header" "$base_header" \
+						| sed -e "s|${past_header}|${past_ref}/${file}|g" \
+						      -e "s|${base_header}|${base_ref:-dirty}/${file}|g"
+					printf "\n"
+				else
+					printf "\n%s did not change between %s and %s...\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
+					printf "It's possible a change to one of the headers it includes caused this error:\n"
+					grep '^#include' "$base_header"
+					printf "\n"
+				fi
+			} | tee "${base_header}.error" >&2
+			return 1
 		fi
 	else
-		# Bits in abidiff's return code can be used to determine the type of error
-		if [ $((ret & 0x1)) -gt 0 ]; then
-			eprintf "error - abidiff did not run properly\n"
-			exit 1
-		fi
+		local ret=0
+		"$ABIDIFF" --non-reachable-types "${past_header}.bin" "${base_header}.bin" > "$log" || ret="$?"
+		if [ "$ret" -eq 0 ]; then
+			if [ "$VERBOSE" = "true" ]; then
+				printf "No ABI differences detected in %s from %s -> %s\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
+			fi
+		else
+			# Bits in abidiff's return code can be used to determine the type of error
+			if [ $((ret & 0x1)) -gt 0 ]; then
+				eprintf "error - abidiff did not run properly\n"
+				exit 1
+			fi
 
-		# If the only changes were additions (not modifications to existing APIs), then
-		# there's no problem. Ignore these diffs.
-		if grep "Unreachable types summary" "$log" | grep -q "0 removed" &&
-		   grep "Unreachable types summary" "$log" | grep -q "0 changed"; then
-			return 0
-		fi
-		{
-			printf "!!! ABI differences detected in %s from %s -> %s !!!\n\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
-			sed  -e '/summary:/d' -e '/changed type/d' -e '/^$/d' -e 's/^/  /g' "$log"
-
-			if ! cmp "$past_header" "$base_header" > /dev/null 2>&1; then
-				printf "\nHeader file diff (after headers_install):\n"
-				diff -Naur "$past_header" "$base_header" \
-					| sed -e "s|${past_header}|${past_ref}/${file}|g" \
-					      -e "s|${base_header}|${base_ref:-dirty}/${file}|g"
-				printf "\n"
-			else
-				printf "\n%s did not change between %s and %s...\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
-				printf "It's possible a change to one of the headers it includes caused this error:\n"
-				grep '^#include' "$base_header"
-				printf "\n"
+			# If the only changes were additions (not modifications to existing APIs), then
+			# there's no problem. Ignore these diffs.
+			if grep "Unreachable types summary" "$log" | grep -q "0 removed" &&
+			   grep "Unreachable types summary" "$log" | grep -q "0 changed"; then
+				return 0
 			fi
-		} | tee "${base_header}.error" >&2
-		return 1
+			{
+				printf "!!! ABI differences detected in %s from %s -> %s !!!\n\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
+				sed  -e '/summary:/d' -e '/changed type/d' -e '/^$/d' -e 's/^/  /g' "$log"
+
+				if ! cmp "$past_header" "$base_header" > /dev/null 2>&1; then
+					printf "\nHeader file diff (after headers_install):\n"
+					diff -Naur "$past_header" "$base_header" \
+						| sed -e "s|${past_header}|${past_ref}/${file}|g" \
+						      -e "s|${base_header}|${base_ref:-dirty}/${file}|g"
+					printf "\n"
+				else
+					printf "\n%s did not change between %s and %s...\n" "$file" "$past_ref" "${base_ref:-dirty tree}"
+					printf "It's possible a change to one of the headers it includes caused this error:\n"
+					grep '^#include' "$base_header"
+					printf "\n"
+				fi
+			} | tee "${base_header}.error" >&2
+			return 1
+		fi
 	fi
 }
 
-- 
2.41.0.255.g8b1d071c50-goog