sessiond: ust: conditionally enable the underscore prefix variant quirk

[lttng-tools.git] / src / bin / lttng-sessiond / ust-app.cpp

diff --git a/src/bin/lttng-sessiond/ust-app.cpp b/src/bin/lttng-sessiond/ust-app.cpp
index 8addb5edacabb5bd9ed2397ab81f276cf5b078fb..11d604ea9a463e7c32126b5189e46707e74f7ce1 100644 (file)
--- a/src/bin/lttng-sessiond/ust-app.cpp
+++ b/src/bin/lttng-sessiond/ust-app.cpp
@@ -7895,3 +7895,30 @@ error:
        rcu_read_unlock();
        return ret;
 }
+
+lsu::ctl_field_quirks ust_app::ctl_field_quirks() const
+{
+       /*
+        * Application contexts are expressed as variants. LTTng-UST announces
+        * those by registering an enumeration named `..._tag`. It then registers a
+        * variant as part of the event context that contains the various possible
+        * types.
+        *
+        * Unfortunately, the names used in the enumeration and variant don't
+        * match: the enumeration names are all prefixed with an underscore while
+        * the variant type tag fields aren't.
+        *
+        * While the CTF 1.8.3 specification mentions that
+        * underscores *should* (not *must*) be removed by CTF readers. Babeltrace
+        * 1.x (and possibly others) expect a perfect match between the names used
+        * by tags and variants.
+        *
+        * When the UNDERSCORE_PREFIXED_VARIANT_TAG_MAPPINGS quirk is enabled,
+        * the variant's fields are modified to match the mappings of its tag.
+        *
+        * From ABI version >= 10.x, the variant fields and tag mapping names
+        * correctly match, making this quirk unnecessary.
+        */
+       return v_major <= 9 ? lsu::ctl_field_quirks::UNDERSCORE_PREFIXED_VARIANT_TAG_MAPPINGS :
+               lsu::ctl_field_quirks::NONE;
+}
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