Add "weak" declarations of symbols used in safestack.h and lhash.h

Only for SunCC for now.

It turns out that some compilers to generate external variants of
unused static inline functions, and if they use other external
symbols, those need to be present as well.  If you then happen to
include one of safestack.h or lhash.h without linking with libcrypto,
the build fails.

Fixes #6912

Signed-off-by: Matthias Kraft <Matthias.Kraft@softwareag.com>

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8087)

include/openssl/lhash.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the Apache License 2.0 (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -210,6 +210,31 @@ DEFINE_LHASH_OF(OPENSSL_CSTRING);
 #  pragma warning (pop)
 # endif
 
+/*
+ * If called without higher optimization (min. -xO3) the Oracle Developer
+ * Studio compiler generates code for the defined (static inline) functions
+ * above.
+ * This would later lead to the linker complaining about missing symbols when
+ * this header file is included but the resulting object is not linked against
+ * the Crypto library (openssl#6912).
+ */
+# ifdef __SUNPRO_C
+#  pragma weak OPENSSL_LH_new
+#  pragma weak OPENSSL_LH_free
+#  pragma weak OPENSSL_LH_insert
+#  pragma weak OPENSSL_LH_delete
+#  pragma weak OPENSSL_LH_retrieve
+#  pragma weak OPENSSL_LH_error
+#  pragma weak OPENSSL_LH_num_items
+#  pragma weak OPENSSL_LH_node_stats_bio
+#  pragma weak OPENSSL_LH_node_usage_stats_bio
+#  pragma weak OPENSSL_LH_stats_bio
+#  pragma weak OPENSSL_LH_get_down_load
+#  pragma weak OPENSSL_LH_set_down_load
+#  pragma weak OPENSSL_LH_doall
+#  pragma weak OPENSSL_LH_doall_arg
+# endif /* __SUNPRO_C */
+
 #ifdef  __cplusplus
 }
 #endif

include/openssl/safestack.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 1999-2017 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1999-2019 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the Apache License 2.0 (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -166,6 +166,41 @@ DEFINE_SPECIAL_STACK_OF_CONST(OPENSSL_CSTRING, char)
 typedef void *OPENSSL_BLOCK;
 DEFINE_SPECIAL_STACK_OF(OPENSSL_BLOCK, void)
 
+/*
+ * If called without higher optimization (min. -xO3) the Oracle Developer
+ * Studio compiler generates code for the defined (static inline) functions
+ * above.
+ * This would later lead to the linker complaining about missing symbols when
+ * this header file is included but the resulting object is not linked against
+ * the Crypto library (openssl#6912).
+ */
+# ifdef __SUNPRO_C
+#  pragma weak OPENSSL_sk_num
+#  pragma weak OPENSSL_sk_value
+#  pragma weak OPENSSL_sk_new
+#  pragma weak OPENSSL_sk_new_null
+#  pragma weak OPENSSL_sk_new_reserve
+#  pragma weak OPENSSL_sk_reserve
+#  pragma weak OPENSSL_sk_free
+#  pragma weak OPENSSL_sk_zero
+#  pragma weak OPENSSL_sk_delete
+#  pragma weak OPENSSL_sk_delete_ptr
+#  pragma weak OPENSSL_sk_push
+#  pragma weak OPENSSL_sk_unshift
+#  pragma weak OPENSSL_sk_pop
+#  pragma weak OPENSSL_sk_shift
+#  pragma weak OPENSSL_sk_pop_free
+#  pragma weak OPENSSL_sk_insert
+#  pragma weak OPENSSL_sk_set
+#  pragma weak OPENSSL_sk_find
+#  pragma weak OPENSSL_sk_find_ex
+#  pragma weak OPENSSL_sk_sort
+#  pragma weak OPENSSL_sk_is_sorted
+#  pragma weak OPENSSL_sk_dup
+#  pragma weak OPENSSL_sk_deep_copy
+#  pragma weak OPENSSL_sk_set_cmp_func
+# endif /* __SUNPRO_C */
+
 # ifdef  __cplusplus
 }
 # endif