Bug 1794063 - Create an SEprinter for printing via printf_stderr r=jonco

Differential Revision: https://phabricator.services.mozilla.com/D158819

js/public/Printer.h

@@ -8,6 +8,7 @@
 #define js_Printer_h
 
 #include "mozilla/Attributes.h"
+#include "mozilla/glue/Debug.h"
 #include "mozilla/Range.h"
 
 #include <stdarg.h>
@@ -272,10 +273,11 @@ class JS_PUBLIC_API StringPrinter : public GenericPrinter {
   // success.
   char* reserve(size_t len);
 
-  // Puts |len| characters from |s| at the current position and
-  // return true on success, false on failure.
+  // Puts |len| characters from |s| at the current position. May OOM, which must
+  // be checked by testing the return value of releaseJS() at the end of
+  // printing.
   virtual void put(const char* s, size_t len) final;
-  using GenericPrinter::put;  // pick up |inline bool put(const char* s);|
+  using GenericPrinter::put;  // pick up |put(const char* s);|
 
   virtual bool canPutFromIndex() const final { return true; }
   virtual void putFromIndex(size_t index, size_t length) final {
@@ -337,10 +339,24 @@ class JS_PUBLIC_API Fprinter final : public GenericPrinter {
   void flush() override;
   void finish();
 
-  // Puts |len| characters from |s| at the current position and
-  // return true on success, false on failure.
-  virtual void put(const char* s, size_t len) override;
-  using GenericPrinter::put;  // pick up |inline bool put(const char* s);|
+  // Puts |len| characters from |s| at the current position. Errors may be
+  // detected with hadOutOfMemory() (which will be set for any fwrite() error,
+  // not just OOM.)
+  void put(const char* s, size_t len) override;
+  using GenericPrinter::put;  // pick up |put(const char* s);|
+};
+
+// SEprinter, print using printf_stderr (goes to Android log, Windows debug,
+// else just stderr).
+class SEprinter final : public GenericPrinter {
+ public:
+  constexpr SEprinter() {}
+
+  // Puts |len| characters from |s| at the current position. Ignores errors.
+  virtual void put(const char* s, size_t len) override {
+    printf_stderr("%.*s", int(len), s);
+  }
+  using GenericPrinter::put;  // pick up |put(const char* s);|
 };
 
 // LSprinter, is similar to Sprinter except that instead of using an
@@ -373,10 +389,9 @@ class JS_PUBLIC_API LSprinter final : public GenericPrinter {
   // Drop the current string, and let them be free with the LifoAlloc.
   void clear();
 
-  // Puts |len| characters from |s| at the current position and
-  // return true on success, false on failure.
+  // Puts |len| characters from |s| at the current position.
   virtual void put(const char* s, size_t len) override;
-  using GenericPrinter::put;  // pick up |inline bool put(const char* s);|
+  using GenericPrinter::put;  // pick up |put(const char* s);|
 };
 
 // Escaping printers work like any other printer except that any added character