cppmagic: Conditionals

Implement CPPMAGIC_IFELSE which operates similar to the C ? : operator, but
is evaluated at preprocessing time.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

diff --git a/ccan/cppmagic/cppmagic.h b/ccan/cppmagic/cppmagic.h
index c4454e776392f4edff78ff8289d432ce4e09ddf4..b5c35782f78ca5e58ab16fa45bddb0649c87333c 100644 (file)
--- a/ccan/cppmagic/cppmagic.h
+++ b/ccan/cppmagic/cppmagic.h
@@ -84,4 +84,18 @@
 #define CPPMAGIC_ISEMPTY(...)          \
        CPPMAGIC_ISZERO(CPPMAGIC_NONEMPTY(__VA_ARGS__))
 
 #define CPPMAGIC_ISEMPTY(...)          \
        CPPMAGIC_ISZERO(CPPMAGIC_NONEMPTY(__VA_ARGS__))
 

+/*
+ * CPPMAGIC_IFELSE - preprocessor conditional
+ *
+ * CPPMAGIC_IFELSE(@cond)(@if)(@else)
+ *     expands to @else if @cond is '0', otherwise expands to @if
+ */
+#define _CPPMAGIC_IF_0(...)            _CPPMAGIC_IF_0_ELSE
+#define _CPPMAGIC_IF_1(...)            __VA_ARGS__ _CPPMAGIC_IF_1_ELSE
+#define _CPPMAGIC_IF_0_ELSE(...)       __VA_ARGS__
+#define _CPPMAGIC_IF_1_ELSE(...)
+#define _CPPMAGIC_IFELSE(cond_)                CPPMAGIC_GLUE2(_CPPMAGIC_IF_, cond_)
+#define CPPMAGIC_IFELSE(cond_)         \
+       _CPPMAGIC_IFELSE(CPPMAGIC_NONZERO(cond_))
+

 #endif /* CCAN_CPPMAGIC_H */
 #endif /* CCAN_CPPMAGIC_H */

diff --git a/ccan/cppmagic/test/run.c b/ccan/cppmagic/test/run.c
index fb2bfb9f95450d0354385843be722c462c25a9a2..0f8917d6a4afa5d8e620504a197fd7ae14cec7b8 100644 (file)
--- a/ccan/cppmagic/test/run.c
+++ b/ccan/cppmagic/test/run.c
@@ -17,7 +17,7 @@ static inline void check1(const char *orig, const char *expand,
 
 int main(void)
 {
 
 int main(void)
 {

-       plan_tests(21);
+       plan_tests(24);

 
        CHECK1(CPPMAGIC_NOTHING(), "");
        CHECK1(CPPMAGIC_GLUE2(a, b), "ab");
 
        CHECK1(CPPMAGIC_NOTHING(), "");
        CHECK1(CPPMAGIC_GLUE2(a, b), "ab");


@@ -47,6 +47,10 @@ int main(void)
        CHECK1(CPPMAGIC_ISEMPTY(0), "0");
        CHECK1(CPPMAGIC_ISEMPTY(a, b, c), "0");
        
        CHECK1(CPPMAGIC_ISEMPTY(0), "0");
        CHECK1(CPPMAGIC_ISEMPTY(a, b, c), "0");
        

+       CHECK1(CPPMAGIC_IFELSE(0)(abc)(def), "def");
+       CHECK1(CPPMAGIC_IFELSE(1)(abc)(def), "abc");
+       CHECK1(CPPMAGIC_IFELSE(not zero)(abc)(def), "abc");
+

        /* This exits depending on whether all tests passed */
        return exit_status();
 }
        /* This exits depending on whether all tests passed */
        return exit_status();
 }