[libcamera-devel] [PATCH v1 2/2] libcamera: base: utils: Support C libraries lacking locale support

[Laurent Pinchart]

Not all C libraries include support for locale objects (locale_t) and
the strto*_l() family of functions. A notable example is uClibc that can
be compiled with a hardcoded "C" locale. Compilation then fails as the
newlocale(), freelocale() and strtod_l() functions are not defined.

Fix the compilation breakage by checking for the availability of
newlocale(), and fall back to strtod() when the function isn't
available. This may not lead to the correct result if support for locale
objects isn't available and the locale isn't hardcoded to "C", but that
is such a corner case that we will likely never encounter it.

Fixes: e8ae254970cf ("libcamera: yaml_parser: Use C locale")
Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 meson.build                  |  4 ++++
 src/libcamera/base/utils.cpp | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/meson.build b/meson.build
index e86673dd5c0c..7dcd34d3e6b3 100644
--- a/meson.build
+++ b/meson.build
@@ -72,6 +72,10 @@ if cc.has_header_symbol('unistd.h', 'issetugid')
     config_h.set('HAVE_ISSETUGID', 1)
 endif
 
+if cc.has_header_symbol('locale.h', 'newlocale', prefix : '#define _GNU_SOURCE')
+    config_h.set('HAVE_NEWLOCALE', 1)
+endif
+
 if cc.has_header_symbol('stdlib.h', 'secure_getenv', prefix : '#define _GNU_SOURCE')
     config_h.set('HAVE_SECURE_GETENV', 1)
 endif
diff --git a/src/libcamera/base/utils.cpp b/src/libcamera/base/utils.cpp
index 4a239427a4d9..ac3e1311995e 100644
--- a/src/libcamera/base/utils.cpp
+++ b/src/libcamera/base/utils.cpp
@@ -464,6 +464,8 @@ std::string toAscii(const std::string &str)
  * \a b
  */
 
+#if HAVE_NEWLOCALE
+
 namespace {
 
 /*
@@ -493,6 +495,8 @@ Locale cLocale("C");
 
 } /* namespace */
 
+#endif /* HAVE_NEWLOCALE */
+
 /**
  * \brief Convert a string to a double independently of the current locale
  * \param[in] nptr The string to convert
@@ -506,7 +510,15 @@ Locale cLocale("C");
  */
 double strtod(const char *__restrict nptr, char **__restrict endptr)
 {
+#if HAVE_NEWLOCALE
 	return strtod_l(nptr, endptr, cLocale.locale());
+#else
+	/*
+	 * If the libc implementation doesn't provide locale object support,
+	 * assume that strtod() is locale-independent.
+	 */
+	return strtod(nptr, endptr);
+#endif
 }
 
 } /* namespace utils */
-- 
Regards,

Laurent Pinchart