diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index 81c0229fb846..85fd67a3c4a6 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -288,6 +288,7 @@ def has_header_symbol(self, hname, symbol, prefix, env, extra_args=None, depende
             #ifndef {symbol}
                 {symbol};
             #endif
+            return 0;
         }}'''
         return self.compiles(t.format(**fargs), env, extra_args, dependencies)
 
@@ -452,6 +453,7 @@ def cross_sizeof(self, typename, prefix, env, extra_args=None, dependencies=None
         {prefix}
         int main(int argc, char **argv) {{
             {type} something;
+            return 0;
         }}'''
         if not self.compiles(t.format(**fargs), env, extra_args, dependencies):
             return -1
@@ -484,6 +486,7 @@ def cross_alignment(self, typename, prefix, env, extra_args=None, dependencies=N
         {prefix}
         int main(int argc, char **argv) {{
             {type} something;
+            return 0;
         }}'''
         if not self.compiles(t.format(**fargs), env, extra_args, dependencies):
             return -1
@@ -554,6 +557,7 @@ def get_return_value(self, fname, rtype, prefix, env, extra_args, dependencies):
         #include <stdio.h>
         int main(int argc, char *argv[]) {{
             printf ("{fmt}", {cast} {f}());
+            return 0;
         }}'''.format(**fargs)
         res = self.run(code, env, extra_args, dependencies)
         if not res.compiled:
@@ -704,6 +708,7 @@ def has_function(self, funcname, prefix, env, extra_args=None, dependencies=None
                 #error "No definition for __builtin_{func} found in the prefix"
             #endif
         #endif
+            return 0;
         }}'''
         return self.links(t.format(**fargs), env, extra_args, dependencies)