Update podspec for boringssl prefixing

templates/gRPC-Core.podspec.template

@@ -175,7 +175,7 @@
       ss.libraries = 'z'
       ss.dependency "#{s.name}/Interface", version
       ss.dependency 'BoringSSL-GRPC', '0.0.5'
-      ss.compiler_flags = '-DGRPC_SHADOW_BORINGSSL_SYMBOLS'
+      ss.compiler_flags = '-DBORINGSSL_PREFIX=GRPC'
 
       ss.source_files = ${ruby_multiline_list(grpc_private_files(libs), 22)}
 

templates/src/objective-c/BoringSSL-GRPC.podspec.template

@@ -1,8 +1,6 @@
 %YAML 1.2
 --- |
   <%!
-    def expand_symbol_list(symbol_list):
-        return ',\n    '.join("'#define %s GRPC_SHADOW_%s'" % (symbol, symbol) for symbol in symbol_list)
     import subprocess
     boringssl_commit = subprocess.check_output(['git', 'rev-parse', 'HEAD'], cwd='third_party/boringssl').decode().strip()
   %>
@@ -119,7 +117,7 @@
 
     # We don't need to inhibit all warnings; only -Wno-shorten-64-to-32. But Cocoapods' linter doesn't
     # want that for some reason.
-    s.compiler_flags = '-DOPENSSL_NO_ASM', '-GCC_WARN_INHIBIT_ALL_WARNINGS', '-w'
+    s.compiler_flags = '-DOPENSSL_NO_ASM', '-GCC_WARN_INHIBIT_ALL_WARNINGS', '-w', '-DBORINGSSL_PREFIX=GRPC'
     s.requires_arc = false
 
     # Like many other C libraries, BoringSSL has its public headers under `include/<libname>/` and its
@@ -225,25 +223,14 @@
       % endfor
       EOF
 
-      # The symbol prefixing mechanism is performed by redefining BoringSSL symbols with "#define
-      # SOME_BORINGSSL_SYMBOL GRPC_SHADOW_SOME_BORINGSSL_SYMBOL". Unfortunately, some symbols are
-      # already redefined as macros in BoringSSL headers in the form "#define SOME_BORINGSSL_SYMBOL
-      # SOME_BORINGSSL_SYMBOL" Such type of redefinition will cause "SOME_BORINGSSL_SYMBOL redefined"
-      # error when using together with our prefix header. So the workaround in the below lines removes
-      # all such type of #define directives.
-      sed -i'.back' '/^#define \\([A-Za-z0-9_]*\\) \\1/d' include/openssl/*.h
-      # Remove lines of the format below for the same reason above
-      #     #define SOME_BORINGSSL_SYMBOL ${"\\"}
-      #         SOME_BORINGSSL_SYMBOL
-      sed -i'.back' '/^#define.*\\\\$/{N;/^#define \\([A-Za-z0-9_]*\\) *\\\\\\n *\\1/d;}' include/openssl/*.h
+      # Grab prefix header from GCS
+      curl -o include/openssl/boringssl_prefix_symbols.h https://storage.googleapis.com/grpc_boringssl_prefix_headers/boringssl_prefix_symbols-${boringssl_commit}.h
 
       # We are renaming openssl to openssl_grpc so that there is no conflict with openssl if it exists
       find . -type f \\( -path '*.h' -or -path '*.cc' -or -path '*.c' \\) -print0 | xargs -0 -L1 sed -E -i'.grpc_back' 's;#include <openssl/;#include <openssl_grpc/;g'
-    END_OF_COMMAND
+      # BoringSSL include boringssl_prefix_symbols.h without any prefix, which does not match the
 
-    # Redefine symbols to avoid conflict when the same app also depends on OpenSSL. The list of
-    # symbols are src/objective-c/grpc_shadow_boringssl_symbol_list.
-    # This is the last part of this file.
-    s.prefix_header_contents = 
-      ${expand_symbol_list(settings.grpc_shadow_boringssl_symbols)}
+      # Xcode import style. We add it here so that Xcode knows where to find it.
+      find . -type f \\( -path '*.h' -or -path '*.cc' -or -path '*.c' \\) -print0 | xargs -0 -L1 sed -E -i'.grpc_back' 's;#include <boringssl_prefix_symbols.h>;#include <openssl_grpc/boringssl_prefix_symbols.h>;g'
+    END_OF_COMMAND
   end