Add thunk logic to the hphpi binary

Summary:
This diff adds thunk logic so that we can make the hphpi binary redirect
to another binary via execv(). The idea here is that we can set a symlink
"/.hphpi-thunk" on individual machines to make hphpi redirect to a different
binary.

Note that the thunk will only be triggered for the hphpi binary, and only
if "/.hphpi-thunk" exists in the filesystem. Other binaries produced by
hphpc will not trigger the thunk and will continue to behave the same as
before.

Blame Rev:

Reviewers: je, kma, mwilliams, qigao, oyamauchi

CC:

Test Plan:
fast_tests
slow_tests
Verify the thunk is triggered for the hphpi binary
Vierfy the thunk is not triggered for other binaries
Build www and browse the site

Revert Plan:

Differential Revision: 340844

bin/run.mk

@@ -22,6 +22,10 @@ endif
 
 -include sep_extensions.mk
 
+ifdef HPHPI_THUNK
+CPPFLAGS += -DTHUNK_FILENAME='"/.hphpi-thunk"'
+endif
+
 CPPFLAGS += -I. $(SEP_EXTENSION_INCLUDE_PATHS)
 LIBS = $(SEP_EXTENSION_LIBS) $(HPHP_LIB)/libhphp_runtime.a $(ALL_LIBS)
 

src/compiler/analysis/analysis_result.cpp

@@ -4571,6 +4571,9 @@ void AnalysisResult::outputCPPMain() {
   cg_printf("\n");
   cg_printf("#ifndef HPHP_BUILD_LIBRARY\n");
   cg_indentBegin("int main(int argc, char** argv) {\n");
+  cg_indentBegin("#ifdef THUNK_FILENAME\n");
+  cg_printf("DO_THUNK(THUNK_FILENAME, argv);\n");
+  cg_indentEnd("#endif\n");
   cg_printf("return HPHP::execute_program(argc, argv);\n");
   cg_indentEnd("}\n");
   cg_printf("#endif\n");

src/hphpi/Makefile

@@ -15,7 +15,8 @@ all: $(HPHPI)
 
 $(HPHPI): $(HPHP) $(PHP_FILES)
 	@echo "Compiling hphpi..."
-	$(V)$(if $(OUT_TOP),HPHP_LIB=$(LIB_DIR)) $(HPHP) \
+	$(V)$(if $(OUT_TOP),HPHP_LIB=$(LIB_DIR)) HPHPI_THUNK=1 \
+		$(HPHP) \
 		-t cpp -f exe --input-dir . \
 		-i $(PHP_FILES) -o $(OUT_DIR)gen \
 		-vEnableEval=2 --log=1 \

src/runtime/base/macros.h

@@ -451,6 +451,12 @@ do { \
     }                                           \
   } while(0)                                    \
 
+#define DO_THUNK(thunkFilename, argv) {         \
+  if (strlen(thunkFilename) > 0) {              \
+    execv(thunkFilename, argv);                 \
+  }                                             \
+}
+
 //////////////////////////////////////////////////////////////////////////////
 }