Fix the C library initialization to avoid calling static C++ constructors twice.
The problem was due to the fact that, in the case of dynamic executables,
the dynamic linker calls the DT_PREINIT_ARRAY, DT_INIT and DT_INIT_ARRAY
constructors when loading shared libraries and dynamic executables,
*before* calling the executable's entry point (i.e. arch-$ARCH/bionic/crtbegin_dynamic.c)
which in turns call __libc_init() in libc.so, as defined by bionic/libc_init_dynamic.c
The latter did call these constructors array again, mistakenly.
The patch also updates the documentation of many related functions.
Also adds a new section to linker/README.TXT explaining restrictions on
C library usage.
The patch has been tested on a Dream for stability issues with
proprietary blobs:
- H264 decoding works
- Camera + Video recording works
- GPS works
- Sensors work
The tests in system/extra/tests/bionic/libc/common/test_static_cpp_mutex.cpp has been
run and shows the static C++ constructor being called only once.
diff --git a/libc/arch-x86/bionic/crtbegin_dynamic.S b/libc/arch-x86/bionic/crtbegin_dynamic.S
index 3b47b18..b013641 100644
--- a/libc/arch-x86/bionic/crtbegin_dynamic.S
+++ b/libc/arch-x86/bionic/crtbegin_dynamic.S
@@ -29,25 +29,35 @@
.type _start, @function
.globl _start
-# this is the small startup code that is first run when
-# any executable that is statically-linked with Bionic
-# runs.
+# This is the small startup code that is called from
+# the dynamic linker to execute an executable once all
+# dependent shared libraries have been loaded and
+# initialized.
#
-# it's purpose is to call __libc_init with appropriate
+# It's purpose is to call __libc_init as defined in
+# bionic/libc_init_dynamic.c with appropriate
# arguments, which are:
#
# - the address of the raw data block setup by the Linux
# kernel ELF loader
#
-# - address of an "onexit" function, not used on any
-# platform supported by Bionic
+# - address of an "onexit" function (not used on any
+# platform supported by Bionic)
#
# - address of the "main" function of the program. We
# can't hard-code it in the adr pseudo instruction
# so we use a tiny trampoline that will get relocated
# by the dynamic linker before this code runs
#
-# - address of the constructor list
+# - address of the constructors table, i.e. a table
+# that points to various initialization and
+# finalization sections for the program.
+#
+# NOTE: This code is currently placed in shared libraries
+# by the build system, but will be ignored.
+#
+# On the other hand, the arrays defined below are
+# required and will be parsed by the dynamic linker.
#
_start:
mov %esp, %eax