C front-end: Section/ASM renaming also needs to be applied to aliases

The example taken from the Linux kernel shows that people mix weak
aliases with section attributes. Not updating the alias name results in
a namespace lookup failure.

gcc_attributes11 is a reduced example taken from SV-COMP, where the same problem
arises.

Author: tautschnig

regression/ansi-c/gcc_attributes11/main.c

@@ -0,0 +1,18 @@
+#ifdef __GNUC__
+// example extracted from SV-COMP's ldv-linux-3.4-simple/
+// 32_7_cpp_false-unreach-call_single_drivers-net-phy-dp83640
+static int __attribute__((__section__(".init.text")))
+__attribute__((no_instrument_function)) dp83640_init(void)
+{
+  return 0;
+}
+int init_module(void) __attribute__((alias("dp83640_init")));
+#endif
+
+int main()
+{
+#ifdef __GNUC__
+  dp83640_init();
+#endif
+  return 0;
+}

regression/ansi-c/gcc_attributes11/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.c
+
+^EXIT=0$
+^SIGNAL=0$
+--
+^warning: ignoring
+^CONVERSION ERROR$

regression/ansi-c/gcc_attributes9/main.c

@@ -11,11 +11,23 @@ const char* __attribute__((section("s"))) __attribute__((weak)) bar();
 volatile int __attribute__((__section__(".init.data1"))) txt_heap_base1;
 volatile int __attribute__((__section__(".init.data3"))) txt_heap_base, __attribute__((__section__(".init.data4"))) txt_heap_size;
 
+int __attribute__((__section__(".init.text"))) __attribute__((__cold__))
+__alloc_bootmem_huge_page(void *h);
+int __attribute__((__section__(".init.text"))) __attribute__((__cold__))
+alloc_bootmem_huge_page(void *h);
+int alloc_bootmem_huge_page(void *h)
+  __attribute__((weak, alias("__alloc_bootmem_huge_page")));
+int __alloc_bootmem_huge_page(void *h)
+{
+  return 1;
+}
 #endif
 
 int main()
 {
 #ifdef __GNUC__
+  int r = alloc_bootmem_huge_page(0);
+
   static int __attribute__((section(".data.unlikely"))) __warned;
   __warned=1;
   return __warned;

src/ansi-c/c_typecheck_base.cpp

@@ -708,7 +708,12 @@ void c_typecheck_baset::typecheck_declaration(
 
         // alias function need not have been declared yet, thus
         // can't lookup
-        symbol.value=symbol_exprt(full_spec.alias);
+        // also cater for renaming/placement in sections
+        const auto &renaming_entry = asm_label_map.find(full_spec.alias);
+        if(renaming_entry == asm_label_map.end())
+          symbol.value = symbol_exprt(full_spec.alias);
+        else
+          symbol.value = symbol_exprt(renaming_entry->second);
         symbol.is_macro=true;
       }