[PATCH] eal: fix function versioning with LTO

[Stephen Hemminger <stephen@networkplumber.org>]

When using function versioning and building with Link Time Optimization,
the compiler does not see the __asm__ annotation of symbols and
therefore thinks there are two versions of the same symbol.

The fix is to use compiler symver attribute on the function which
was added in GCC 10. Keep the older method for backward compatibility
with older compilers.

Bugzilla ID: 1949
Fixes: e30e194c4d06 ("eal: rework function versioning macros")
Cc: stable@dpdk.org

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/eal/common/eal_export.h | 46 +++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 12 deletions(-)

diff --git a/lib/eal/common/eal_export.h b/lib/eal/common/eal_export.h
index 7e47d34064..1318e6278d 100644
--- a/lib/eal/common/eal_export.h
+++ b/lib/eal/common/eal_export.h
@@ -30,39 +30,61 @@
  * new functionality, behavior, etc.  When that occurs, it is desirable to
  * allow for backwards compatibility for a time with older binaries that are
  * dynamically linked to the dpdk.
+ *
+ * RTE_VERSION_SYMBOL
+ * Create a symbol version table entry binding symbol <name>@DPDK_<ver> to the internal
+ * function name <name>_v<ver>.
+ *
+ * RTE_VERSION_EXPERIMENTAL_SYMBOL similar to RTE_VERSION_SYMBOL but for experimental API symbols.
+ * This is mainly used for keeping compatibility for symbols that get promoted to stable ABI.
+ *
+ * RTE_DEFAULT_SYMBOL
+ * Create a symbol version entry instructing the linker to bind references to
+ * symbol <name> to the internal symbol <name>_v<ver>.
  */
 
 #ifdef RTE_BUILD_SHARED_LIB
 
-/*
- * Create a symbol version table entry binding symbol <name>@DPDK_<ver> to the internal
- * function name <name>_v<ver>.
- */
+/* Prefer the compiler method of versioning which uses attributes */
+#if  __has_attribute(symver)
+
+#define RTE_VERSION_SYMBOL(ver, type, name, args) VERSIONING_WARN	\
+	__attribute__((__symver__(RTE_STR(name) "@DPDK_" RTE_STR(ver)))) \
+	type name ## _v ## ver args;					\
+	type name ## _v ## ver args
+
+#define RTE_VERSION_EXPERIMENTAL_SYMBOL(type, name, args) VERSIONING_WARN \
+	__attribute__((__symver__(RTE_STR(name) "@EXPERIMENTAL")))	\
+	type name ## _exp args;						\
+	type name ## _exp args
+
+#define RTE_DEFAULT_SYMBOL(ver, type, name, args) VERSIONING_WARN	\
+	__attribute__((__symver__(RTE_STR(name) "@@DPDK_" RTE_STR(ver)))) \
+	type name ## _v ## ver args;					\
+	type name ## _v ## ver args
+#else /* !__has_attribute(symver) */
+
+/* Use asm tag to create symbol table entry */
 #define RTE_VERSION_SYMBOL(ver, type, name, args) VERSIONING_WARN \
 __asm__(".symver " RTE_STR(name) "_v" RTE_STR(ver) ", " RTE_STR(name) "@DPDK_" RTE_STR(ver)); \
 __rte_used type name ## _v ## ver args; \
 type name ## _v ## ver args
 
-/*
- * Similar to RTE_VERSION_SYMBOL but for experimental API symbols.
- * This is mainly used for keeping compatibility for symbols that get promoted to stable ABI.
- */
 #define RTE_VERSION_EXPERIMENTAL_SYMBOL(type, name, args) VERSIONING_WARN \
 __asm__(".symver " RTE_STR(name) "_exp, " RTE_STR(name) "@EXPERIMENTAL") \
 __rte_used type name ## _exp args; \
 type name ## _exp args
 
-/*
- * Create a symbol version entry instructing the linker to bind references to
- * symbol <name> to the internal symbol <name>_v<ver>.
- */
 #define RTE_DEFAULT_SYMBOL(ver, type, name, args) VERSIONING_WARN \
 __asm__(".symver " RTE_STR(name) "_v" RTE_STR(ver) ", " RTE_STR(name) "@@DPDK_" RTE_STR(ver)); \
 __rte_used type name ## _v ## ver args; \
 type name ## _v ## ver args
 
+#endif /* __has_attribute(symver) */
+
 #else /* !RTE_BUILD_SHARED_LIB */
 
+/* static library does not have versioned symbols */
 #define RTE_VERSION_SYMBOL(ver, type, name, args) VERSIONING_WARN \
 type name ## _v ## ver args; \
 type name ## _v ## ver args
-- 
2.53.0