[PATCH v2 26/30] build: Disable weak symbols for MSYS2

[Simon Glass]

Weak symbols are not well supported by the PE format, so disable them.
We need to manually ensure that only one function is present in the source
code.

Add a Kconfig option to control this and enable it when building for
Windows.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

(no changes since v1)

 Kconfig                             | 12 ++++++++++++
 include/linux/compiler_attributes.h |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/Kconfig b/Kconfig
index 9ac816abef1c..985b09680934 100644
--- a/Kconfig
+++ b/Kconfig
@@ -75,6 +75,18 @@ config CLANG_VERSION
 config CC_IS_MSYS
 	def_bool $(success,uname -o | grep -q Msys)
 
+config WEAK_SYMBOLS
+	bool "Enable use of weak symbols"
+	default y if !CC_IS_MSYS
+	help
+	  The Portable Executable (PE) format used by Windows does not support
+	  weak symbols very well. Even where it can be made to work, the __weak
+	  function attribute cannot be made to work with PE. Supporting weak
+	  symbols would involve changing the source code in undesirable ways.
+
+	  This option controls whether weak symbols are used, or not. When
+	  disabled, the __weak function attribute does nothing.
+
 choice
 	prompt "Optimization level"
 	default CC_OPTIMIZE_FOR_SIZE
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index 44c9a08d7346..c954109a065b 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -268,6 +268,10 @@
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
  */
+#ifdef CONFIG_WEAK_SYMBOLS
 #define __weak                          __attribute__((__weak__))
+#else
+#define __weak
+#endif
 
 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */
-- 
2.40.1.495.gc816e09b53d-goog