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Wrap sprintf()/snprintf() macros to prevent expansion errors.

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Previously, FORTIFY_SOURCE used single macros to define these standard
functions for use with clang. This can cause conflicts with other macros used
to call these functions, particularly when those macros expand the number of
arguments to the function. This change wraps our macro definitions, so that
expansion properly takes place for programmer arguments first.

Change-Id: I55929b1fd2a643b9d14a17631c4bcab3b0b712cf
This commit is contained in:
Stephen Hines 2013-10-11 00:45:24 -07:00
parent eda2679e30
commit 6e38072add
2 changed files with 22 additions and 2 deletions
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6
libc/include/stdio.h
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@ -469,7 +469,8 @@ int vsprintf(char *dest, const char *format, __va_list ap)
}
#if defined(__clang__)
#define snprintf(dest, size, ...) __builtin___snprintf_chk(dest, size, 0, __bos(dest), __VA_ARGS__)
#define __wrap_snprintf(dest, size, ...) __builtin___snprintf_chk(dest, size, 0, __bos(dest), __VA_ARGS__)
#define snprintf(...) __wrap_snprintf(__VA_ARGS__)
#else
__BIONIC_FORTIFY_INLINE
__printflike(3, 4)
@ -481,7 +482,8 @@ int snprintf(char *dest, size_t size, const char *format, ...)
#endif
#if defined(__clang__)
#define sprintf(dest, ...) __builtin___sprintf_chk(dest, 0, __bos(dest), __VA_ARGS__)
#define __wrap_sprintf(dest, ...) __builtin___sprintf_chk(dest, 0, __bos(dest), __VA_ARGS__)
#define sprintf(...) __wrap_sprintf(__VA_ARGS__)
#else
__BIONIC_FORTIFY_INLINE
__printflike(2, 3)

18
tests/fortify_test.cpp
View File

@ -825,3 +825,21 @@ TEST(TEST_NAME, memcpy_chk_max_int_size) {
ASSERT_EQ('8', buf[8]);
ASSERT_EQ('\0', buf[9]);
}
// Verify that macro expansion is done properly for sprintf/snprintf (which
// are defined as macros in stdio.h under clang).
#define CONTENTS "macro expansion"
#define BUF_AND_SIZE(A) A, sizeof(A)
#define BUF_AND_CONTENTS(A) A, CONTENTS
#define BUF_AND_SIZE_AND_CONTENTS(A) A, sizeof(A), CONTENTS
TEST(TEST_NAME, s_n_printf_macro_expansion) {
char buf[BUFSIZ];
snprintf(BUF_AND_SIZE(buf), CONTENTS);
EXPECT_STREQ(CONTENTS, buf);
snprintf(BUF_AND_SIZE_AND_CONTENTS(buf));
EXPECT_STREQ(CONTENTS, buf);
sprintf(BUF_AND_CONTENTS(buf));
EXPECT_STREQ(CONTENTS, buf);
}