Zbigniew Jędrzejewski-Szmek
52abc9fe96
asprintf is nice to use, but the _documented_ error return convention is unclear: > If memory allocation wasn't possible, or some other error occurs, > these functions will return -1, and the contents of strp are undefined. What exactly "undefined" means is up for debate: if it was really undefined, the caller wouldn't be able to meaningfully clean up, because they wouldn't know if strp is a valid pointer. So far we interpreted "undefined" — in some parts of the code base — as "either NULL or a valid pointer that needs to be freed", and — in other parts of the codebase — as "always NULL". I checked glibc and musl, and they both uncoditionally set the output pointer to NULL on failure. There is also no information _why_ asprintf failed. It could be an allocation error or format string error. But we just don't have this information. Let's add a wrapper that either returns a good string or a NULL pointer. Since there's just one failure result, we don't need a separate return value and an output argument and can simplify callers.
73 lines
4.0 KiB
C
73 lines
4.0 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#pragma once
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#include <printf.h>
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#include <stdio.h>
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#include "basic-forward.h"
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_printf_(3, 4)
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static inline char* snprintf_ok(char *buf, size_t len, const char *format, ...) {
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va_list ap;
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int r;
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va_start(ap, format);
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r = vsnprintf(buf, len, format, ap);
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va_end(ap);
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return r >= 0 && (size_t) r < len ? buf : NULL;
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}
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#define xsprintf(buf, fmt, ...) \
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assert_message_se(snprintf_ok(buf, ELEMENTSOF(buf), fmt, ##__VA_ARGS__), "xsprintf: buffer too small")
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char* asprintf_safe(const char *restrict fmt, ...) _printf_(1, 2);
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#define VA_FORMAT_ADVANCE(format, ap) \
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do { \
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int _argtypes[128]; \
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size_t _i, _k; \
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/* See https://github.com/google/sanitizers/issues/992 */ \
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if (HAS_FEATURE_MEMORY_SANITIZER) \
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memset(_argtypes, 0, sizeof(_argtypes)); \
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_k = parse_printf_format((format), ELEMENTSOF(_argtypes), _argtypes); \
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assert(_k < ELEMENTSOF(_argtypes)); \
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for (_i = 0; _i < _k; _i++) { \
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if (_argtypes[_i] & PA_FLAG_PTR) { \
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(void) va_arg(ap, void*); \
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continue; \
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} \
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\
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switch (_argtypes[_i]) { \
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case PA_INT: \
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case PA_INT|PA_FLAG_SHORT: \
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case PA_CHAR: \
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(void) va_arg(ap, int); \
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break; \
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case PA_INT|PA_FLAG_LONG: \
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(void) va_arg(ap, long int); \
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break; \
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case PA_INT|PA_FLAG_LONG_LONG: \
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(void) va_arg(ap, long long int); \
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break; \
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case PA_WCHAR: \
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(void) va_arg(ap, wchar_t); \
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break; \
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case PA_WSTRING: \
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case PA_STRING: \
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case PA_POINTER: \
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(void) va_arg(ap, void*); \
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break; \
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case PA_FLOAT: \
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case PA_DOUBLE: \
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(void) va_arg(ap, double); \
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break; \
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case PA_DOUBLE|PA_FLAG_LONG_DOUBLE: \
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(void) va_arg(ap, long double); \
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break; \
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default: \
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assert_not_reached(); \
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} \
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} \
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} while (false)
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