nginx-util: do not use fallthrough attribute

[peter-stadler]

Maintainer: me
Compile tested: x86_64, x86_64 qemu, master
Run tested: x86_64, x86_64 qemu, master, run tests

Description: fix compile warning/error (issue #15653)

[ptpt52]

looks like a wrong fix

[peter-stadler]

Do you know a better method? Else: It should work, duplicating the code instead of falling through ...

[ptpt52]

try this:

diff --git a/net/nginx-util/src/nginx-ssl-util.hpp b/net/nginx-util/src/nginx-ssl-util.hpp
index 4f12925db..b52346b7f 100644
--- a/net/nginx-util/src/nginx-ssl-util.hpp
+++ b/net/nginx-util/src/nginx-ssl-util.hpp
@@ -166,8 +166,10 @@ static constexpr auto _escape = _Line{
         std::string ret{};
         for (char c : strptr) {
             switch (c) {
-                case '^': ret += '\\'; [[fallthrough]];
-                case '_': [[fallthrough]];
+                case '^': ret += '\\';
+                         /* fallthrough */
+                case '_':
+                         /* fallthrough */
                 case '-': ret += c; break;
                 default:
                     if ((isalpha(c) != 0) || (isdigit(c) != 0)) {

do not use [[fallthrough]]

[ptpt52]

or more simple:

diff --git a/net/nginx-util/src/nginx-ssl-util.hpp b/net/nginx-util/src/nginx-ssl-util.hpp
index 4f12925db..4484b3550 100644
--- a/net/nginx-util/src/nginx-ssl-util.hpp
+++ b/net/nginx-util/src/nginx-ssl-util.hpp
@@ -166,8 +166,8 @@ static constexpr auto _escape = _Line{
         std::string ret{};
         for (char c : strptr) {
             switch (c) {
-                case '^': ret += '\\'; [[fallthrough]];
-                case '_': [[fallthrough]];
+                case '^': ret += '\\'; /* fallthrough */
+                case '_': /* fallthrough */
                 case '-': ret += c; break;
                 default:
                     if ((isalpha(c) != 0) || (isdigit(c) != 0)) {

[peter-stadler]

I changed it, thank you :-)
Do you happen to know why the [[fallthrough]]; attribute is not working anymore?

[ptpt52]

it is likely

fallthrough;

work?

https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html

https://stackoverflow.com/questions/45349079/how-to-use-attribute-fallthrough-correctly-in-gcc

[peter-stadler]

I thought about the c++17 standard attribute not the legacy one, but it is not that important ...

[peter-stadler]

I am not sure if the comment /* fallthrough */ would work with gcc 10, so I copy the ret += c; break; instead of falling through.

(The command fallthrough; would work, too, but AFAIK it is not standard c++ and clang-tidy is not recognizing it. So I hesitate using it here.)