Enhance Py_ARRAY_LENGTH(): fail at build time if the argument is not an array

Victor Stinner · Victor Stinner · commit dfb866d127c8 · 2011-09-29T01:12:24.000+02:00
Move other various macros to pymcacro.h

Thanks Rusty Russell for having written these amazing C macros!
diff --git a/Include/Python.h b/Include/Python.h
@@ -48,6 +48,7 @@
 #include <assert.h>
 
 #include "pyport.h"
+#include "pymacro.h"
 
 #include "pyatomic.h"
 
@@ -126,24 +127,6 @@
 #include "pystrcmp.h"
 #include "dtoa.h"
 #include "fileutils.h"
-
-/* Argument must be a char or an int in [-128, 127] or [0, 255]. */
-#define Py_CHARMASK(c) ((unsigned char)((c) & 0xff))
-
 #include "pyfpe.h"
 
-/* Define macros for inline documentation. */
-#define PyDoc_VAR(name) static char name[]
-#define PyDoc_STRVAR(name,str) PyDoc_VAR(name) = PyDoc_STR(str)
-#ifdef WITH_DOC_STRINGS
-#define PyDoc_STR(str) str
-#else
-#define PyDoc_STR(str) ""
-#endif
-
-#define Py_ARRAY_LENGTH(array) (sizeof(array) / sizeof((array)[0]))
-
-#define Py_MIN(x, y) (((x) > (y)) ? (y) : (x))
-#define Py_MAX(x, y) (((x) > (y)) ? (x) : (y))
-
 #endif /* !Py_PYTHON_H */
diff --git a/Include/pymacro.h b/Include/pymacro.h
@@ -0,0 +1,57 @@
+#ifndef Py_PYMACRO_H
+#define Py_PYMACRO_H
+
+#define Py_MIN(x, y) (((x) > (y)) ? (y) : (x))
+#define Py_MAX(x, y) (((x) > (y)) ? (x) : (y))
+
+/* Argument must be a char or an int in [-128, 127] or [0, 255]. */
+#define Py_CHARMASK(c) ((unsigned char)((c) & 0xff))
+
+
+/* Assert a build-time dependency, as an expression.
+
+   Your compile will fail if the condition isn't true, or can't be evaluated
+   by the compiler. This can be used in an expression: its value is 0.
+
+   Example:
+
+   #define foo_to_char(foo)  \
+       ((char *)(foo)        \
+        + Py_BUILD_ASSERT(offsetof(struct foo, string) == 0))
+
+   Written by Rusty Russell, public domain. */
+#define Py_BUILD_ASSERT(cond) \
+    (sizeof(char [1 - 2*!(cond)]) - 1)
+
+#if defined(__GNUC__)
+/* Two gcc extensions.
+   &a[0] degrades to a pointer: a different type from an array */
+#define _Py_ARRAY_LENGTH_CHECK(array) \
+    Py_BUILD_ASSERT(!__builtin_types_compatible_p(typeof(array), \
+                                                  typeof(&(array)[0])))
+#else
+#define _Py_ARRAY_LENGTH_CHECK(array) 0
+#endif
+
+
+/* Get the number of elements in a visible array
+
+   This does not work on pointers, or arrays declared as [], or function
+   parameters. With correct compiler support, such usage will cause a build
+   error (see Py_BUILD_ASSERT).
+
+   Written by Rusty Russell, public domain. */
+#define Py_ARRAY_LENGTH(array) \
+    (sizeof(array) / sizeof((array)[0]) + _Py_ARRAY_LENGTH_CHECK(array))
+
+
+/* Define macros for inline documentation. */
+#define PyDoc_VAR(name) static char name[]
+#define PyDoc_STRVAR(name,str) PyDoc_VAR(name) = PyDoc_STR(str)
+#ifdef WITH_DOC_STRINGS
+#define PyDoc_STR(str) str
+#else
+#define PyDoc_STR(str) ""
+#endif
+
+#endif /* Py_PYMACRO_H */
diff --git a/Makefile.pre.in b/Makefile.pre.in
@@ -493,7 +493,7 @@ $(PYTHONFRAMEWORKDIR)/Versions/$(VERSION)/$(PYTHONFRAMEWORK): \
 		-install_name $(DESTDIR)$(PYTHONFRAMEWORKINSTALLDIR)/Versions/$(VERSION)/$(PYTHONFRAMEWORK) \
 		-compatibility_version $(VERSION) \
 		-current_version $(VERSION) \
-		-framework CoreFoundation $(LIBS); 
+		-framework CoreFoundation $(LIBS);
 	$(INSTALL) -d -m $(DIRMODE)  \
 		$(PYTHONFRAMEWORKDIR)/Versions/$(VERSION)/Resources/English.lproj
 	$(INSTALL_DATA) $(RESSRCDIR)/Info.plist \
@@ -718,6 +718,7 @@ PYTHON_HEADERS= \
 		Include/pyfpe.h \
 		Include/pymath.h \
 		Include/pygetopt.h \
+		Include/pymacro.h \
 		Include/pymem.h \
 		Include/pyport.h \
 		Include/pystate.h \
diff --git a/Misc/ACKS b/Misc/ACKS
@@ -825,6 +825,7 @@ Rauli Ruohonen
 Jeff Rush
 Sam Rushing
 Mark Russell
+Rusty Russell
 Nick Russo
 Patrick Sabin
 Sébastien Sablé
diff --git a/PCbuild/pythoncore.vcproj b/PCbuild/pythoncore.vcproj
@@ -886,6 +886,10 @@
 				RelativePath="..\Include\pytime.h"
 				>
 			</File>
+			<File
+				RelativePath="..\Include\pymacro.h"
+				>
+			</File>
 			<File
 				RelativePath="..\Include\pymem.h"
 				>

Original file line number	Diff line number	Diff line change
`@@ -886,6 +886,10 @@`
`886`	`886`	`RelativePath="..\Include\pytime.h"`
`887`	`887`	`>`
`888`	`888`	`</File>`
	`889`	`+ <File`
	`890`	`+ RelativePath="..\Include\pymacro.h"`
	`891`	`+ >`
	`892`	`+ </File>`
`889`	`893`	`<File`
`890`	`894`	`RelativePath="..\Include\pymem.h"`
`891`	`895`	`>`