lib/io/fprintf.h: [v]fprintec(): Add functions

These functions print a formatted string, followed by a colon and
a space, followed by an error string produced by strerror($2).  That is,
the output is as follows:

	fmt: error message string

For example,
	fprintec(stderr, ENOMEM, "foo(%d)", 42);
prints
	foo(42): Cannot allocate memory

These functions return the number of characters printed, or a negative
value on error, like fprintf(3).

Signed-off-by: Alejandro Colomar <alx@kernel.org>

diff --git a/lib/Makefile.am b/lib/Makefile.am
index 599cb0bbdd4bd827db48e93c5e3512da30ed7060..2995cca66cc4dd21d80d1b88bea015f264bf9d5c 100644 (file)
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -105,6 +105,8 @@ libshadow_la_SOURCES = \
        idmapping.c \
        io/fgets/fgets.c \
        io/fgets/fgets.h \
+       io/fprintf.c \
+       io/fprintf.h \
        io/syslog.c \
        io/syslog.h \
        isexpired.c \

diff --git a/lib/io/fprintf.c b/lib/io/fprintf.c
new file mode 100644 (file)
index 0000000..452d8dd
--- /dev/null
+++ b/lib/io/fprintf.c
@@ -0,0 +1,16 @@
+// SPDX-FileCopyrightText: 2025, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#include "config.h"
+
+#include "io/fprintf.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+
+
+extern inline int fprintec(FILE *restrict stream, int e,
+    const char *restrict fmt, ...);
+extern inline int vfprintec(FILE *restrict stream, int e,
+    const char *restrict fmt, va_list ap);

diff --git a/lib/io/fprintf.h b/lib/io/fprintf.h
new file mode 100644 (file)
index 0000000..356d721
--- /dev/null
+++ b/lib/io/fprintf.h
@@ -0,0 +1,63 @@
+// SPDX-FileCopyrightText: 2025, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#ifndef SHADOW_INCLUDE_LIB_IO_FPRINTF_H_
+#define SHADOW_INCLUDE_LIB_IO_FPRINTF_H_
+
+
+#include "config.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "attr.h"
+
+
+format_attr(printf, 3, 4)
+inline int fprintec(FILE *restrict stream, int e,
+    const char *restrict fmt, ...);
+format_attr(printf, 3, 0)
+inline int vfprintec(FILE *restrict stream, int e,
+    const char *restrict fmt, va_list ap);
+
+
+// fprintec - FILE* print errno code
+inline int
+fprintec(FILE *restrict stream, int e, const char *restrict fmt, ...)
+{
+       int      len;
+       va_list  ap;
+
+       va_start(ap, fmt);
+       len = vfprintec(stream, e, fmt, ap);
+       va_end(ap);
+
+       return len;
+}
+
+
+// vfprintec - va_list FILE* print errno code
+inline int
+vfprintec(FILE *restrict stream, int e, const char *restrict fmt, va_list ap)
+{
+       int  l1, l2, l3;
+
+       l1 = vfprintf(stream, fmt, ap);
+       if (l1 < 0)
+               return l1;
+
+       l2 = fprintf(stream, l1 ? ": " : "");
+       if (l2 < 0)
+               return l2;
+
+       l3 = fprintf(stream, "%s\n", strerror(e));
+       if (l3 < 0)
+               return l3;
+
+       return l1 + l2 + l3;
+}
+
+
+#endif  // include guard