Created attachment 22046 [details] _configtest.i When building the Python NumPy library for Python 3.x, it does the following test compilation test: typedef struct {float __x; float __y;} npy_check_sizeof_type; int main () { static int test_array [1 - 2 * !(((long) (sizeof (npy_check_sizeof_type))) <= 16.0)]; test_array [0] = 0 ... This code compiles fine with GCC 4.4.5 on Ubuntu, but fails with GCC 4.5.1 on Arch Linux x86_64: % gcc _configtest.c _configtest.c: In function 'main': _configtest.c:5:16: error: storage size of 'test_array' isn't constant % gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-unknown-linux-gnu/4.5.1/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: ../configure --prefix=/usr --enable-languages=c,c++,fortran,objc,obj-c++,ada --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --enable-gnu-unique-object --enable-lto --enable-plugin --disable-multilib --disable-libstdcxx-pch --with-system-zlib --with-ppl --with-cloog --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info Thread model: posix gcc version 4.5.1 (GCC)
16.0 is a floating point number which I think is causing the issue.
Comeau C/C++ gives the following error message for the above testcase: "ComeauTest.c", line 5: error: expression must have integral type <= 16.0)];
Note that you can't trivially extend the laxity in /* Handle a size folded to an integer constant but not an integer constant expression. */ if (!size_int_const) { /* If this is a file scope declaration of an ordinary identifier, this is invalid code; diagnosing it here and not subsequently treating the type as variable-length avoids more confusing diagnostics later. */ if ((decl_context == NORMAL || decl_context == FIELD) && current_scope == file_scope) pedwarn (input_location, 0, "variably modified %qE at file scope", name); else this_size_varies = size_varies = true; warn_variable_length_array (name, size); } (that does a pedwarn rather than an error if this occurs at file scope) to the present case of a static array inside a function, because it's valid to have a block scope static *pointer* to VLA (which is however different from a pointer to non-VLA), so you'd need to be lax only if it's a static array rather than a pointer to such.
This fails, too: "error: storage size of ‘sv’ isn’t constant" int main(void) { const int len = 20; static char sv[len]; } Similarly, gcc 4.4 accepted #define CONST_STRING "aaa" static char x[strlen(CONST_STRING)]; but gcc-4.5 does not. (Of course, I could overload "strlen" ... but whether that's enough reason to reject that?)