Make libstdc++'s complex and complex.h modular.

In C++11, this was already essentially the case. C++11 simply removes the C99
<complex.h> and does not make its facilities available. That is a fine and
reasonable stance and I've preserved it. I've also removed the unconditional
(and dead) undef that was breaking modular builds of the <complex> header.

The question is what should <complex.h> and <complex> do in C++98. Currently
these two headers conspire to undef 'complex' only when both are included. This
doesn't actually work well as it relies on non-modular behavior of observing
the order of inclusion. My proposed solution is to simply make including both
<complex> and <complex.h> in the same file an error in C++98. This error
remains non-modular, but is phrased in a way that should not preclude building
this code with modules. In a modular build, the polite error simply won't
trigger and instead the user will be faced with a compile error if they ever
try to use 'complex' as something other than a macro expanding to '_Complex'.
Eventually, we can use an explicit conflict marking in a modules map or other
tool to surface this kind of error even to modules builds.



git-svn-id: https://gcc.gnu.org/svn/gcc/branches/google/gcc-4_9@222074 138bc75d-0d04-0410-961f-82ee72b054a4

5 files changed, 38 insertions, 12 deletions

diff --git a/contrib/testsuite-management/aarch64-grtev4-linux-gnu.xfail b/contrib/testsuite-management/aarch64-grtev4-linux-gnu.xfail
index a2a027e5338..a459149ee01 100644
--- a/contrib/testsuite-management/aarch64-grtev4-linux-gnu.xfail
+++ b/contrib/testsuite-management/aarch64-grtev4-linux-gnu.xfail
@@ -18,6 +18,10 @@ FAIL: gcc.dg/wself-assign-1.c (test for warnings, line 20)
 FAIL: gcc.dg/wself-assign-1.c (test for warnings, line 21)
 FAIL: gcc.dg/wself-assign-1.c (test for warnings, line 22)
 
+# Also xfailed in x86; Google b/20184248
+FAIL: 17_intro/headers/c++1998/complex.cc (test for excess errors)
+FAIL: 26_numerics/complex/c99.cc (test for excess errors)
+
 # AArch64-specific; appear to be missing "loop turned into non-loop; it never loops" output.
 FAIL: gcc.dg/unroll_1.c (test for warnings, line 14)
 FAIL: gcc.dg/unroll_1.c (test for warnings, line 24)
diff --git a/contrib/testsuite-management/powerpc64le-grtev4-linux-gnu.xfail b/contrib/testsuite-management/powerpc64le-grtev4-linux-gnu.xfail
index 410cdb94311..d8995e0cd1f 100644
--- a/contrib/testsuite-management/powerpc64le-grtev4-linux-gnu.xfail
+++ b/contrib/testsuite-management/powerpc64le-grtev4-linux-gnu.xfail
@@ -18,6 +18,10 @@ FAIL: gcc.dg/wself-assign-1.c (test for warnings, line 20)
 FAIL: gcc.dg/wself-assign-1.c (test for warnings, line 21)
 FAIL: gcc.dg/wself-assign-1.c (test for warnings, line 22)
 
+# Also xfailed in x86; Google b/20184248
+FAIL: 17_intro/headers/c++1998/complex.cc (test for excess errors)
+FAIL: 26_numerics/complex/c99.cc (test for excess errors)
+
 # PPCle-specific.  From PR33512, still failing in truck despite resolved PR.
 FAIL: gcc.dg/and-1.c scan-assembler-not nand
 
diff --git a/contrib/testsuite-management/x86_64-grtev4-linux-gnu.xfail b/contrib/testsuite-management/x86_64-grtev4-linux-gnu.xfail
index a6eb7eca038..b4fa6933791 100644
--- a/contrib/testsuite-management/x86_64-grtev4-linux-gnu.xfail
+++ b/contrib/testsuite-management/x86_64-grtev4-linux-gnu.xfail
@@ -21,6 +21,10 @@ FAIL: gcc.dg/wself-assign-1.c (test for warnings, line 22)
 # http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60037
 FAIL: ext/random/hypergeometric_distribution/operators/values.cc execution test
 
+# Google b/20184248
+FAIL: 17_intro/headers/c++1998/complex.cc (test for excess errors)
+FAIL: 26_numerics/complex/c99.cc (test for excess errors)
+
 # Google b/14137212
 FAIL: 29_atomics/atomic/cons/user_pod.cc (test for excess errors)
 
diff --git a/libstdc++-v3/include/c_compatibility/complex.h b/libstdc++-v3/include/c_compatibility/complex.h
index d072b68a835..b15361ea0d5 100644
--- a/libstdc++-v3/include/c_compatibility/complex.h
+++ b/libstdc++-v3/include/c_compatibility/complex.h
@@ -26,21 +26,29 @@
  *  This is a Standard C++ Library header.
  */
 
-#include <bits/c++config.h>
+#ifndef _GLIBCXX_COMPLEX_H
+#define _GLIBCXX_COMPLEX_H 1
 
 #if __cplusplus >= 201103L
 # include <ccomplex>
+#else // C++98 and C++03
+
+// The C++ <complex> header is incompatible with the C99 <complex.h> header,
+// they cannot be included into a single translation unit portably. Notably,
+// C++11's <ccomplex> does not include C99's <complex.h> and in C++11's
+// <complex.h> is defined to provide only what C++11's <ccomplex> does in a
+// different namespace.
+#ifdef _GLIBCXX_COMPLEX
+# error Cannot include both <complex> and C99's <complex.h>
 #endif
 
-#if _GLIBCXX_HAVE_COMPLEX_H
-# include_next <complex.h>
-# ifdef _GLIBCXX_COMPLEX
-// See PR56111, keep the macro in C++03 if possible.
-#  undef complex
-# endif
-#endif
+// Delegate to a system complex.h if we don't provide it as part of the C++
+// implementation.
+#include_next <complex.h>
 
-#ifndef _GLIBCXX_COMPLEX_H
-#define _GLIBCXX_COMPLEX_H 1
+// Provide a define indicating that a C99-style <complex.h> has been included.
+#define _GLIBCXX_C99_COMPLEX_H
+
+#endif // C++98 and C++03
 
 #endif
diff --git a/libstdc++-v3/include/std/complex b/libstdc++-v3/include/std/complex
index 941e6b7d845..3104b584eb6 100644
--- a/libstdc++-v3/include/std/complex
+++ b/libstdc++-v3/include/std/complex
@@ -44,8 +44,14 @@
 #include <cmath>
 #include <sstream>
 
-// Get rid of a macro possibly defined in <complex.h>
-#undef complex
+// The C++ <complex> header is incompatible with the C99 <complex.h> header,
+// they cannot be included into a single translation unit portably. Notably,
+// C++11's <ccomplex> does not include C99's <complex.h> and in C++11's
+// <complex.h> is defined to provide only what C++11's <ccomplex> does in a
+// different namespace.
+#ifdef _GLIBCXX_C99_COMPLEX_H
+#error Cannot include both <complex> and C99's <complex.h>
+#endif
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {