[Bug math/10415] New: Compiler error when compiling test-tgmath2.c with gcc 4.5.0 (20090717) + fix

["dps at simpson dot demon dot co dot uk" <sourceware-bugzilla at sourceware dot org>]

This bug also affects the i686-pc-linux-gnu target and probably most other
targets In make check gcc 4.5.0 says:

test-tgmath2.c: In function ?test?:
test-tgmath2.c:167:3: error: assignment of read-only variable ?texpr?
test-tgmath2.c:168:3: error: assignment of read-only variable ?texpr?
test-tgmath2.c:169:3: error: assignment of read-only variable ?texpr?
test-tgmath2.c:178:3: error: assignment of read-only variable ?texpr?
test-tgmath2.c:179:3: error: assignment of read-only variable ?texpr?

My diagnosis that __typeof__ (expr) texpr declares texpr to be const in those
tests, so the assignment further down in the TEST2 macro produces an error message.

The following patch uses mixed declarations and code to eliminate the
assignment, which fixes the problem. It might be nice if the compiler supported
declaring a variable as const and allowing a single assignment to it sometime later.

--- math/test-tgmath2.c.dist    2009-07-19 17:22:48.664507445 +0100
+++ math/test-tgmath2.c 2009-07-19 19:24:45.952008134 +0100
@@ -120,13 +120,12 @@
 #define TEST2(expr, type, rettype, fn) \
   do                                                           \
     {                                                          \
-      __typeof__ (expr) texpr = 0;                             \
       TEST_TYPE_ONLY (expr, rettype);                          \
       if (count != 0)                                          \
        FAIL ("internal error");                                \
       if (counts[T##type][C_##fn] != 0)                                \
        FAIL ("internal error");                                \
-      texpr = expr;                                            \
+      __typeof__ (expr) texpr = expr;                          \
       __asm __volatile ("" : : "r" (&texpr));                  \
       if (count != 1 || counts[T##type][C_##fn] != 1)          \
        {                                                       \

-- 
           Summary: Compiler error when compiling test-tgmath2.c with  gcc
                    4.5.0 (20090717) + fix
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: aj at suse dot de
        ReportedBy: dps at simpson dot demon dot co dot uk
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://sourceware.org/bugzilla/show_bug.cgi?id=10415

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