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author | Gregory Nutt <gnutt@nuttx.org> | 2014-12-08 10:40:06 -0600 |
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committer | Gregory Nutt <gnutt@nuttx.org> | 2014-12-08 10:40:06 -0600 |
commit | c14f202a2c98fd55c472ac64f98fc049457cf35d (patch) | |
tree | 92a09f80a7bbd9c2160d3c7e6c50d99cd51b0f57 | |
parent | 4e112873b66a66875c2a7c45ab1454467e64f219 (diff) | |
download | nuttx-c14f202a2c98fd55c472ac64f98fc049457cf35d.tar.gz nuttx-c14f202a2c98fd55c472ac64f98fc049457cf35d.tar.bz2 nuttx-c14f202a2c98fd55c472ac64f98fc049457cf35d.zip |
avsprintf(): Fix a bug in usage of va_list on x86. On x86, va_list is a pointer to a single copy on the stack. avsprintf() calls lib_vsprintf() twice and so traverses the va_list twice using va_start. va_start modifies that single copy on the stack so that the second call to lib_vsprintf() fails. This appears to be an issue with x86 only so far
-rw-r--r-- | nuttx/libc/stdio/lib_avsprintf.c | 33 |
1 files changed, 30 insertions, 3 deletions
diff --git a/nuttx/libc/stdio/lib_avsprintf.c b/nuttx/libc/stdio/lib_avsprintf.c index 29ea969d4..6f9e5cb77 100644 --- a/nuttx/libc/stdio/lib_avsprintf.c +++ b/nuttx/libc/stdio/lib_avsprintf.c @@ -47,6 +47,24 @@ /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ +/* On some architectures, va_list is really a pointer to a structure on the + * stack. And the va_arg builtin will modify that instance of va_list. Since + * avsprintf traverse the parameters in the va_list twice, the va_list will + * be altered in this first cases and the second usage will fail. So far, I + * have seen this only on the X86 family with GCC. + */ + +#undef CLONE_APLIST +#define ap1 ap +#define ap2 ap + +#if defined(CONFIG_ARCH_X86) +# define CLONE_APLIST 1 +# undef ap2 +#elif defined(CONFIG_ARCH_SIM) && (defined(CONFIG_HOST_X86) || defined(CONFIG_HOST_X86_64)) +# define CLONE_APLIST 1 +# undef ap2 +#endif /**************************************************************************** * Private Type Declarations @@ -98,17 +116,26 @@ int avsprintf(FAR char **ptr, const char *fmt, va_list ap) { struct lib_outstream_s nulloutstream; struct lib_memoutstream_s memoutstream; +#ifdef CLONE_APLIST + va_list ap2; +#endif FAR char *buf; int nbytes; DEBUGASSERT(ptr && fmt); - /* First, use a nullstream to get the size of the buffer. The number +#ifdef CLONE_APLIST + /* Clone the va_list so that the contents of the input values are not altered */ + + va_copy(ap2, ap); +#endif + +/* First, use a nullstream to get the size of the buffer. The number * of bytes returned may or may not include the null terminator. */ lib_nulloutstream(&nulloutstream); - nbytes = lib_vsprintf((FAR struct lib_outstream_s *)&nulloutstream, fmt, ap); + nbytes = lib_vsprintf((FAR struct lib_outstream_s *)&nulloutstream, fmt, ap1); /* Then allocate a buffer to hold that number of characters, adding one * for the null terminator. @@ -131,7 +158,7 @@ int avsprintf(FAR char **ptr, const char *fmt, va_list ap) /* Then let lib_vsprintf do it's real thing */ nbytes = lib_vsprintf((FAR struct lib_outstream_s *)&memoutstream.public, - fmt, ap); + fmt, ap2); /* Return a pointer to the string to the caller. NOTE: the memstream put() * method has already added the NUL terminator to the end of the string (not |