use C99 standard for compiling C code

Closes #1833.

diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa871e6a1414d0e45e8d6222ebf23b66dcd3865c..feaa8fc239f28a4692ab89ae82f77f39f991e82d 100644 (file)
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - CentOS/RHEL 6 is no longer supported
 - Vestiges of Qt4 support have been removed
 - C++11 support is now required of the C++ compiler used to build Graphviz
+- C99 support is now required of the C compiler used to build Graphviz
 
 ### Fixed
 - memory leak in label construction

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 59db6211fbec47eaa7e57796188a2b2e1d5da9a1..923e111d2cc463dd836df93d64ec649d82b9c667 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -174,6 +174,9 @@ add_custom_target(uninstall
 
 # =========================== Compiler configuration ===========================
 
+set(CMAKE_C_STANDARD 99)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 

diff --git a/configure.ac b/configure.ac
index 6577caf1c7fa91ea86b6e71e6191093f7c5aeb75..3f8c7078992446b5f5125349f2a907d5c0be6312 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -310,6 +310,9 @@ dnl checks for compilers
 
 AM_PROG_CC_C_O
 AC_PROG_CC_C99
+if test "x$ac_cv_prog_cc_c99" = "xno"; then
+  AC_MSG_ERROR([C compiler does not support C99])
+fi
 AC_PROG_CXX
 AX_CXX_COMPILE_STDCXX_11(noext,mandatory)
 AC_PROG_OBJC

diff --git a/rtest/test_examples.py b/rtest/test_examples.py
index 1d6de61ce66323e534d6042deae8b4be929b0c94..2d665e945ac90a164a82604c8c9dca8b1d12192e 100644 (file)
--- a/rtest/test_examples.py
+++ b/rtest/test_examples.py
@@ -44,7 +44,7 @@ def test_compile_example(src):
         subprocess.check_call([cc, filepath, '-Fe:', exe, '-nologo',
           rt_lib_option, '-link'] + ['{}.lib'.format(l) for l in libs])
       else:
-        subprocess.check_call([cc, '-o', exe, filepath]
+        subprocess.check_call([cc, '-std=c99', '-o', exe, filepath]
           + ['-l{}'.format(l) for l in libs])
 
       # FIXME: Remove skip of execution of neatopack.c example when

diff --git a/rtest/test_regression.py b/rtest/test_regression.py
index df27f1397182b3bd22045b103c9453236ef8e7a2..9b48a1b63060b1e94c3e476a41819405fba47ed4 100644 (file)
--- a/rtest/test_regression.py
+++ b/rtest/test_regression.py
@@ -339,7 +339,8 @@ def test_1767():
             rt_lib_option, '-link', 'cgraph.lib', 'gvc.lib'])
       else:
           cc = os.environ.get('CC', 'cc')
-          subprocess.check_call([cc, c_src, '-o', exe, '-lcgraph', '-lgvc'])
+          subprocess.check_call([cc, '-std=c99', c_src, '-o', exe, '-lcgraph',
+            '-lgvc'])
 
       # find our co-located dot input
       dot = os.path.abspath(os.path.join(os.path.dirname(__file__), '1767.dot'))