[Support] Change fatal_error_handler_t to take a const char* instead of std::string

https://commondatastorage.googleapis.com/chromium-browser-clang/llvm-include-analysis.html

Excessive use of the <string> header has a massive impact on compile time; its most commonly included via the ErrorHandling.h header, which has to be included in many key headers, impacting many source files that have no need for std::string.

As an initial step toward removing the <string> include from ErrorHandling.h, this patch proposes to update the fatal_error_handler_t handler to just take a raw const char* instead.

The next step will be to remove the report_fatal_error std::string variant, which will involve a lot of cleanup and better use of Twine/StringRef.

Differential Revision: https://reviews.llvm.org/D111049

clang/tools/clang-repl/ClangRepl.cpp

@@ -32,7 +32,7 @@ static llvm::cl::list<std::string> OptInputs(llvm::cl::Positional,
                                              llvm::cl::ZeroOrMore,
                                              llvm::cl::desc("[code to run]"));
 
-static void LLVMErrorHandler(void *UserData, const std::string &Message,
+static void LLVMErrorHandler(void *UserData, const char *Message,
                              bool GenCrashDiag) {
   auto &Diags = *static_cast<clang::DiagnosticsEngine *>(UserData);
 

clang/tools/driver/cc1_main.cpp

@@ -57,7 +57,7 @@ using namespace llvm::opt;
 // Main driver
 //===----------------------------------------------------------------------===//
 
-static void LLVMErrorHandler(void *UserData, const std::string &Message,
+static void LLVMErrorHandler(void *UserData, const char *Message,
                              bool GenCrashDiag) {
   DiagnosticsEngine &Diags = *static_cast<DiagnosticsEngine*>(UserData);
 

clang/tools/driver/cc1as_main.cpp

@@ -550,7 +550,7 @@ static bool ExecuteAssembler(AssemblerInvocation &Opts,
   return Failed;
 }
 
-static void LLVMErrorHandler(void *UserData, const std::string &Message,
+static void LLVMErrorHandler(void *UserData, const char *Message,
                              bool GenCrashDiag) {
   DiagnosticsEngine &Diags = *static_cast<DiagnosticsEngine*>(UserData);
 

clang/tools/libclang/FatalErrorHandler.cpp

@@ -11,11 +11,11 @@
 #include "llvm/Support/ErrorHandling.h"
 #include <stdlib.h>
 
-static void aborting_fatal_error_handler(void *, const std::string &reason,
+static void aborting_fatal_error_handler(void *, const char *reason,
                                          bool) {
   // Write the result out to stderr avoiding errs() because raw_ostreams can
   // call report_fatal_error.
-  fprintf(stderr, "LIBCLANG FATAL ERROR: %s\n", reason.c_str());
+  fprintf(stderr, "LIBCLANG FATAL ERROR: %s\n", reason);
   ::abort();
 }
 

llvm/include/llvm/Support/ErrorHandling.h

@@ -18,12 +18,12 @@
 #include <string>
 
 namespace llvm {
-class StringRef;
+  class StringRef;
   class Twine;
 
   /// An error handler callback.
   typedef void (*fatal_error_handler_t)(void *user_data,
-                                        const std::string& reason,
+                                        const char *reason,
                                         bool gen_crash_diag);
 
   /// install_fatal_error_handler - Installs a new error handler to be used

llvm/lib/Support/ErrorHandling.cpp

@@ -105,7 +105,7 @@ void llvm::report_fatal_error(const Twine &Reason, bool GenCrashDiag) {
   }
 
   if (handler) {
-    handler(handlerData, Reason.str(), GenCrashDiag);
+    handler(handlerData, Reason.str().c_str(), GenCrashDiag);
   } else {
     // Blast the result out to stderr.  We don't try hard to make sure this
     // succeeds (e.g. handling EINTR) and we can't use errs() here because
@@ -218,11 +218,11 @@ void llvm::llvm_unreachable_internal(const char *msg, const char *file,
 #endif
 }
 
-static void bindingsErrorHandler(void *user_data, const std::string& reason,
+static void bindingsErrorHandler(void *user_data, const char *reason,
                                  bool gen_crash_diag) {
   LLVMFatalErrorHandler handler =
       LLVM_EXTENSION reinterpret_cast<LLVMFatalErrorHandler>(user_data);
-  handler(reason.c_str());
+  handler(reason);
 }
 
 void LLVMInstallFatalErrorHandler(LLVMFatalErrorHandler Handler) {

llvm/tools/llvm-as-fuzzer/llvm-as-fuzzer.cpp

@@ -30,7 +30,7 @@ static jmp_buf JmpBuf;
 
 namespace {
 
-void MyFatalErrorHandler(void *user_data, const std::string& reason,
+void MyFatalErrorHandler(void *user_data, const char *reason,
                          bool gen_crash_diag) {
   // Don't bother printing reason, just return to the test function,
   // since a fatal error represents a successful parse (i.e. it correctly

llvm/tools/llvm-isel-fuzzer/llvm-isel-fuzzer.cpp

@@ -107,7 +107,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   return 0;
 }
 
-static void handleLLVMFatalError(void *, const std::string &Message, bool) {
+static void handleLLVMFatalError(void *, const char *Message, bool) {
   // TODO: Would it be better to call into the fuzzer internals directly?
   dbgs() << "LLVM ERROR: " << Message << "\n"
          << "Aborting to trigger fuzzer exit handling.\n";

llvm/tools/llvm-opt-fuzzer/llvm-opt-fuzzer.cpp

@@ -170,7 +170,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   return 0;
 }
 
-static void handleLLVMFatalError(void *, const std::string &Message, bool) {
+static void handleLLVMFatalError(void *, const char *Message, bool) {
   // TODO: Would it be better to call into the fuzzer internals directly?
   dbgs() << "LLVM ERROR: " << Message << "\n"
          << "Aborting to trigger fuzzer exit handling.\n";