util/disk_cache: Fix disk_cache_get_function_timestamp with disabled cache.

radv always needs it, so just check the header instead. Also
do not declare the function if the variable is not set, so we
get a nice compile error instead of failing to open a device
at runtime.

Fixes: b87ef9e606 "util: fix MSVC build issue in disk_cache.h"
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>

configure.ac

@@ -872,6 +872,7 @@ AC_HEADER_MAJOR
 AC_CHECK_HEADER([xlocale.h], [DEFINES="$DEFINES -DHAVE_XLOCALE_H"])
 AC_CHECK_HEADER([sys/sysctl.h], [DEFINES="$DEFINES -DHAVE_SYS_SYSCTL_H"])
 AC_CHECK_HEADERS([endian.h])
+AC_CHECK_HEADER([dlfcn.h], [DEFINES="$DEFINES -DHAVE_DLFCN_H"])
 AC_CHECK_FUNC([strtof], [DEFINES="$DEFINES -DHAVE_STRTOF"])
 AC_CHECK_FUNC([mkostemp], [DEFINES="$DEFINES -DHAVE_MKOSTEMP"])
 AC_CHECK_FUNC([timespec_get], [DEFINES="$DEFINES -DHAVE_TIMESPEC_GET"])

meson.build

@@ -960,7 +960,7 @@ elif cc.has_header_symbol('sys/mkdev.h', 'major')
   pre_args += '-DMAJOR_IN_MKDEV'
 endif
 
-foreach h : ['xlocale.h', 'sys/sysctl.h', 'linux/futex.h', 'endian.h']
+foreach h : ['xlocale.h', 'sys/sysctl.h', 'linux/futex.h', 'endian.h', 'dlfcn.h']
   if cc.compiles('#include <@0@>'.format(h), name : '@0@'.format(h))
     pre_args += '-DHAVE_@0@'.format(h.to_upper().underscorify())
   endif

src/util/disk_cache.h

@@ -24,7 +24,7 @@
 #ifndef DISK_CACHE_H
 #define DISK_CACHE_H
 
-#ifdef ENABLE_SHADER_CACHE
+#ifdef HAVE_DLFCN_H
 #include <dlfcn.h>
 #endif
 #include <assert.h>
@@ -88,10 +88,10 @@ disk_cache_format_hex_id(char *buf, const uint8_t *hex_id, unsigned size)
    return buf;
 }
 
+#ifdef HAVE_DLFCN_H
 static inline bool
 disk_cache_get_function_timestamp(void *ptr, uint32_t* timestamp)
 {
-#ifdef ENABLE_SHADER_CACHE
    Dl_info info;
    struct stat st;
    if (!dladdr(ptr, &info) || !info.dli_fname) {
@@ -102,10 +102,8 @@ disk_cache_get_function_timestamp(void *ptr, uint32_t* timestamp)
    }
    *timestamp = st.st_mtime;
    return true;
-#else
-   return false;
-#endif
 }
+#endif
 
 /* Provide inlined stub functions if the shader cache is disabled. */