bugreport: add compiler info

To help pinpoint the source of a regression, it is useful to know some
info about the compiler which the user's Git client was built with. By
adding a generic get_compiler_info() in 'compat/' we can choose which
relevant information to share per compiler; to get started, let's
demonstrate the version of glibc if the user built with 'gcc'.

Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Helped-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-bugreport.txt

@@ -27,6 +27,7 @@ The following information is captured automatically:
 
  - 'git version --build-options'
  - uname sysname, release, version, and machine strings
+ - Compiler-specific info string
 
 This tool is invoked via the typical Git setup process, which means that in some
 cases, it might not be able to launch - for example, if a relevant config file

bugreport.c

@@ -4,6 +4,7 @@
 #include "strbuf.h"
 #include "time.h"
 #include "help.h"
+#include "compat/compiler.h"
 
 static void get_system_info(struct strbuf *sys_info)
 {
@@ -25,6 +26,11 @@ static void get_system_info(struct strbuf *sys_info)
 			    uname_info.release,
 			    uname_info.version,
 			    uname_info.machine);
+
+	strbuf_addstr(sys_info, _("compiler info: "));
+	get_compiler_info(sys_info);
+	strbuf_addstr(sys_info, _("libc info: "));
+	get_libc_info(sys_info);
 }
 
 static const char * const bugreport_usage[] = {

compat/compiler.h

@@ -0,0 +1,41 @@
+#ifndef COMPILER_H
+#define COMPILER_H
+
+#include "git-compat-util.h"
+#include "strbuf.h"
+
+#ifdef __GLIBC__
+#include <gnu/libc-version.h>
+#endif
+
+static inline void get_compiler_info(struct strbuf *info)
+{
+	int len = info->len;
+#ifdef __clang__
+	strbuf_addf(info, "clang: %s\n", __clang_version__);
+#elif defined(__GNUC__)
+	strbuf_addf(info, "gnuc: %d.%d\n", __GNUC__, __GNUC_MINOR__);
+#endif
+
+#ifdef _MSC_VER
+	strbuf_addf(info, "MSVC version: %02d.%02d.%05d\n",
+		    _MSC_VER / 100, _MSC_VER % 100, _MSC_FULL_VER % 100000);
+#endif
+
+	if (len == info->len)
+		strbuf_addstr(info, _("no compiler information available\n"));
+}
+
+static inline void get_libc_info(struct strbuf *info)
+{
+	int len = info->len;
+
+#ifdef __GLIBC__
+	strbuf_addf(info, "glibc: %s\n", gnu_get_libc_version());
+#endif
+
+	if (len == info->len)
+		strbuf_addstr(info, _("no libc information available\n"));
+}
+
+#endif /* COMPILER_H */