Set init_priority attribute for global variables in shared lib

The code gets unspecified initializatio order for the global/static
variables in a shared library.

If unluck, a global/static variable may be initialized in *constructor*
function, and then initialized by the default contructor.
For exmaple, if `std::unique_ptr<xxx> var{nullptr};` is initialized in
constructor function, below init order may occur:
1. It is initialized in constructor;
2. Then it is initialized as nullptr;
And eventually when the code is to use the variable, we got nullptr.

We met such issues before on openbmc/openbmc#1581, and the technical
details could be found at [this SO question][1] and [this gcc email][2]

The solution is to specify the init_priority attribute, to make the
global/staic variables inititalize earlier than the contructors.

[1]: https://stackoverflow.com/questions/43941159/global-static-variables-initialization-issue-with-attribute-constructor-i
[2]: https://gcc.gnu.org/ml/gcc-patches/2017-03/msg00863.html

Change-Id: I901a6a5cddec12aec9512fe58b16735fa2ad90d7
Signed-off-by: Lei YU <mine260309@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/chassishandler.cpp b/chassishandler.cpp
index 068ad89..c9885bd 100644
--- a/chassishandler.cpp
+++ b/chassishandler.cpp
@@ -54,7 +54,8 @@ namespace filesystem = std::experimental::filesystem;
 #define SET_PARM_BOOT_FLAGS_VALID_ONE_TIME 0x80
 #define SET_PARM_BOOT_FLAGS_VALID_PERMANENT 0xC0
 
-std::unique_ptr<phosphor::Timer> identifyTimer = nullptr;
+std::unique_ptr<phosphor::Timer> identifyTimer
+    __attribute__((init_priority(101)));
 
 constexpr size_t SIZE_MAC = 18;
 constexpr size_t SIZE_BOOT_OPTION = (uint8_t)