The signature of iconv in SUSv2 and legacy systems used const char** for
the second parameter. We already have a workaround for this in the
<ext/codecvt_specializations.h> header, but were not handling this in
src/c++20/format.cc when using iconv.
Define a concept to check that we can call iconv with a char** and then
use that to decide which type we cast the input pointer to.
libstdc++-v3/ChangeLog:
PR libstdc++/125956
* src/c++20/format.cc [_GLIBCXX_HAVE_ICONV] (iconv_input): New
concept.
(__encoding::conv) [_GLIBCXX_HAVE_ICONV]: Use iconv_input to
decide which type to cast the input pointer to.
---
Tested x86_64-linux.
libstdc++-v3/src/c++20/format.cc | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/src/c++20/format.cc b/libstdc++-v3/src/c++20/format.cc
index 6967d53259da..719d019bc91f 100644
--- a/libstdc++-v3/src/c++20/format.cc
+++ b/libstdc++-v3/src/c++20/format.cc
@@ -58,6 +58,15 @@ struct mutex
};
#endif
+#ifdef _GLIBCXX_HAVE_ICONV
+// Detect whether type T* can be used as the second argument to iconv.
+// SUSv2 used 'const char**', but POSIX.1-2003 uses 'char**'.
+template<typename T>
+ concept iconv_input = requires (::iconv_t cd, T in, size_t n, char** out) {
+ ::iconv(cd, &in, &n, out, &n);
+ };
+#endif
+
// A non-standard locale::facet that caches the locale's std::text_encoding
// and an iconv descriptor for converting from that encoding to UTF-8.
struct __encoding : locale::facet
@@ -111,8 +120,9 @@ struct __encoding : locale::facet
bool done = false;
auto overwrite = [&](char* p, size_t n) {
+ using input_t = __conditional_t<iconv_input<char*>, char*, const char*>;
auto inbytes
- = const_cast<char*>(input.data()) + input.size() - inbytesleft;
+ = const_cast<input_t>(input.data()) + input.size() - inbytesleft;
char* outbytes = p + written;
size_t outbytesleft = n - written;
size_t res = ::iconv(_M_cd, &inbytes, &inbytesleft,
--
2.54.0
