[Qemu-devel] [PATCH] libvixl: Add gcc format attribute

[Stefan Weil <sw@weilnetz.de>]

This helps detecting wrong format strings.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
---

This patch is not intended to be applied before fixing some potential errors.

Addings the GNU gcc format attribute results in lots of compiler errors like these ones:

  CXX   disas/libvixl/a64/disasm-a64.o
disas/libvixl/a64/disasm-a64.cc: In member function ‘int vixl::Disassembler::SubstituteImmediateField(vixl::Instruction*, const char*)’:
disas/libvixl/a64/disasm-a64.cc:1372:66: error: format ‘%d’ expects argument of type ‘int’, but argument 3 has type ‘int64_t {aka long int}’ [-Werror=format]
disas/libvixl/a64/disasm-a64.cc:1421:52: error: format ‘%d’ expects argument of type ‘int’, but argument 3 has type ‘int64_t {aka long int}’ [-Werror=format]
disas/libvixl/a64/disasm-a64.cc:1442:48: error: format ‘%d’ expects argument of type ‘int’, but argument 3 has type ‘int64_t {aka long int}’ [-Werror=format]
disas/libvixl/a64/disasm-a64.cc:1449:42: error: format ‘%d’ expects argument of type ‘int’, but argument 3 has type ‘int64_t {aka long int}’ [-Werror=format]

I don't know the reason, because all locations seem to have arguments
which are function calls, and the called function returns Instr which
is uint32_t, not int64_t.

Stefan

 disas/libvixl/a64/disasm-a64.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/disas/libvixl/a64/disasm-a64.h b/disas/libvixl/a64/disasm-a64.h
index 3a56e15..30df187 100644
--- a/disas/libvixl/a64/disasm-a64.h
+++ b/disas/libvixl/a64/disasm-a64.h
@@ -27,6 +27,7 @@
 #ifndef VIXL_A64_DISASM_A64_H
 #define VIXL_A64_DISASM_A64_H
 
+#include "qemu/compiler.h"      // GCC_FMT_ATTR
 #include "globals.h"
 #include "utils.h"
 #include "instructions-a64.h"
@@ -85,7 +86,7 @@ class Disassembler: public DecoderVisitor {
   bool IsMovzMovnImm(unsigned reg_size, uint64_t value);
 
   void ResetOutput();
-  void AppendToOutput(const char* string, ...);
+  void GCC_FMT_ATTR(2, 3) AppendToOutput(const char* string, ...);
 
   char* buffer_;
   uint32_t buffer_pos_;
-- 
1.7.10.4